How To Clean A Tankless Hot Water Heater

How to Flush a Tankless Water Heater (Step-by-Step Procedure)

Please keep in mind that this content may contain affiliate links. This means that, at no additional cost to you, we may gain a small profit on purchases made via our links. Knowing how to clean a tankless water heatercan assist you in getting the most out of your investment in terms of efficiency and longevity. Consider the following steps in detail, as well as some helpful tools and crucial considerations.

The Importance of Flushing Tankless Models

Tankless water heaters are less expensive and more energy efficient to operate when compared to standard water heaters. They also demand significantly less maintenance and operating area. That is why it is essential to understand first why and when it is necessary, followed by how to flush a tankless water heater, whether it is gas or electric. Examine how the naturally existing sediment in your water impacts the heater, as well as how to make flushing more convenient and safer.

Tankless Water Heaters and Scale Buildup

Anyone who has had a conventional water tank is aware with the necessity of flushing the tank on a regular basis in order to remove sediment. Tankless heaters are not an exception to this rule. Hard water includes minerals that can cause lime scale to build up on the surface of the water. An explosion from the accumulation is less likely with a tankless heater than with a tank model, but it can still result in some expensive complications with a tankless heater. The heat exchanger is particularly susceptible to scale buildup.

This can result in a considerable reduction in the lifespan of this component, as well as a large rise in your electricity expenditures over time.

How Often Should You Flush a Tankless Water Heater?

It is recommended that your tankless water heater be cleansed once a year to keep it operating at peak performance. However, the hardness of your water plays a role in this, and you may find that flushing twice or three times a year is preferable if your home’s water is of very low quality in this regard. To a certain extent, a sediment trap or a water softener can help with hard water.

Isolation Valves

It is critical that we explain isolation valves before proceeding with the rest of the processes. As the name implies, an isolation valve allows you to isolate (isolate) a segment of your pipeline’s liquid or gas supply without having to shut down the entire supply line (as would otherwise be the case). Essentially, the word is equivalent with the term “shut-off valve.” From your stove to your toilet, a wide range of objects in your home are equipped with some type of isolation valve for maintenance or emergency purposes, depending on the item.

In some cases, depending on the manufacturer and if a professional installed your tankless heater, an isolation valve may or may not be put on your tankless heating system.

If your heater does not have this function, we highly advise you to get one installed as soon as possible and to engage a professional to flush the system while you wait, since it may be a significant safety issue while doing a flush or other maintenance tasks.

Using Pumps and Flush Kits

A submersible pump is one of your greatest friends when it comes to flushing a tankless water heater. Instead of enormous volumes of water to sweep up and remove the sediment from a tank heater, a high-quality pump such as the91250 from Superior Pump can save you hours if not days of manual flushing and will save you money in the long run. Flushing will necessitate the use of a large bucket to contain the pump, since there is no easy drainage option available, as there is with a typical tank model, necessitating the use of a submersible model pump.

These kits often include everything you’ll need, including a pump, bucket, descaler, and hoses, among other things.

My favorite kit is made by My PlumbingStuff, and it not only works well and is simple to use, but it is also ecologically friendly down to the last component, making it the greatest tankless water heater flush kit in my opinion.

How to Flush a Gas Tankless Water Heater

Check the owner’s handbook for your water heater, since it may provide specific instructions on how to flush and descale the unit. Rinnai, Rheem, and Noritz are the three most popular manufacturers of gas tankless versions. For your convenience, we’ve included particular guidelines for each of the brands listed below:

  • Procedures for flushing a Rinnai tankless water heater, a Rheem tankless water heater, and a Notritz tankless water heater are all available online.

No matter what type of gas tankless water heater you have, there are a few steps in the flushing process that must be completed in the proper order, but they are all rather straightforward to complete.

Phase 1: Preparation

  1. Disconnect the electrical power source that is feeding the heater. Remove the access panel and check the terminal with a non-contact voltage tester to ensure that there is no longer any power coming through it. Discover where the gas isolation valve is located and close it. To prevent any water from entering the unit while you are working, locate the hot and cold shut-off valves and close them accordingly: To release any pressure, locate the hot water pressure relief valve, which should be located somewhere along the hot water line. Take cautious, because the hot water will be quite hot
  2. The service port for cold water and the service port for hot water will be separate. Hoses should be connected to both of these ports. Fill a five-gallon bucket halfway with water and submerge your submersible pump. The cold water pipe should be connected to your pump. Into the bucket, insert the free end of the hot water line
  3. Pour four gallons of undiluted virgin food-grade white vinegar into a pail and set it aside. In addition, Noritz recommends diluting one gallon of CLR with three gallons of water for heavy-duty applications.

Phase 2: Flushing

  1. Make sure that the hot and cold service ports are open and that the pump is running. Make sure the vinegar is allowed to flow through the heater for at least one hour (longer if the pump runs at less than four gallons per minute). As a result of this, the scale is broken down and the silt is flushed away. Turn off the pump and empty the vinegar into a trash can. Close the cold water service port and disconnect the hose that is connected to it. Open the cold water shutoff valve to let any residual vinegar to be flushed out through the second hose into your bucket for around ten minutes. Close the cold water shut-off valve on your faucet. Allow the water to drain completely before disconnecting the second hose. Close the hot water service port on the boiler. Remove the cold water intake filter as well as the hot water inline filter (if applicable). Remove any retained sediment by flushing the filters with water in a sink.

Phase 3: Cleanup

  1. Reinstall the filter(s) in a secure manner, and then turn off the hot and cold water valves
  2. Replace the access panel
  3. Turn on the gas shutoff valve
  4. And remove the access panel. The electrical supply should be reconnected.

How to Flush an Electric Tankless Water Heater

Flushing out an electric tankless water heater is a little different than cleaning out a gas tankless water heater, and some disassembly may be necessary. Generally speaking, Navien models are easier to understand, however some Takagi models require additional steps in order to properly place the water control valve.

  • Technique for flushing a Navien tankless water heater
  • Procedure for flushing a Takagi tankless water heater

Descaling an electric model is similar to descaling a gas model in that it may be divided into three stages.

Phase 1: Preparation

  1. Switching off the electrical power at the circuit breaker
  2. Close the cold water shut-off valve on your faucet. Open your taps to let any water that has accumulated in the heater to drain
  3. Close the shut-off valve for the hot water supply. Remove the access panel and check the terminal with a non-contact voltage tester to ensure that there is no longer any power coming through it. Disconnect the wires from the heating elements by removing the screws that hold them in place. Extraction of the heating element is accomplished by loosening the hexagonal brass top of the heating element in a counterclockwise manner
  4. Make a visual inspection of the heating components for evidence of damage. A broken element should be replaced as soon as possible. Storage of the heating elements in the cooper chambers of the heater to allow for cleaning of the heating elements

Phase 2: Flushing

  1. Fill the cooper chambers with virgin food-grade white vinegar that has not been diluted
  2. Pour vinegar into the chamber and allow it to rest for 90 minutes to two hours. Using this method, you may break up any scales on the components. Remove the vinegar from the mixture. Replace the heating elements and reattach the cables as necessary. Open the cold water shut-off valve and let the tank to fill up with cold water
  3. Observe the tank for any evidence of leakage (the paper towel test is quite effective in this situation)
  4. To turn off the hot water, turn the shutoff valve. Fill the sink with warm water from various hot water taps and let the water run for about five minutes to flush out the vinegar and remove any air pockets from the line

Phase 3: Cleanup

  1. Turn off all hot water faucets in your home. Close the cold water shut-off valve on your faucet. Clean any dirt from the cold water input filter by flushing the filter under a cold water faucet. Replace the filter in a secure manner. Power should be restored at the breaker once you close the access panel

How to Flush Out a Tankless Hot Water Heater

An on-demand hot water heater, as opposed to a tankless hot water heater, warms water on demand rather than holding it in a storage tank, resulting in significant energy savings. Tankless water heater manufacturers recommend that their units be cleansed at least once a year in order to prevent the buildup of calcium and other minerals within the unit – and even more frequently if you have hard water – to ensure that the device operates efficiently. There are certain units that have an indicator that the unit needs to be flushed.


  • Then, at the breaker panel, turn off the electrical circuit that serves the water heater. To turn off the gas to the water heater if it is powered by a gas heater, spin the gas cutoff counterclockwise around the device.


  • Remove the cover plate from the water heater unit using a screwdriver in order to get access to the wiring within the unit. To test the wiring coming into the terminals, place the tip of a non-contact electrical tester against the wires. As long as the tester light is illuminated, keep turning off circuit breakers or the main circuit breaker for the home until checking all cables reveals that no power is being delivered to the system. Remove the cover plate and replace it.


  • The water supply valve that supplies cold water to the water heater should be turned off. Turn off the main hot-water valve, which is responsible for delivering hot water to the local fixture or many fixtures across the home.


  • Using a 6-foot garden hose, connect the output of a pond pump or sump pump to one end of the hose and the other end of the hose to a cold-water isolation valve. Connect a second garden hose to the hot-water isolation valve to complete the installation. An adjustable wrench should be used to tighten the garden hose couplers.


  • Fill a 5-gallon bucket halfway with water and add the pump and open end of the second hose. Fill the bucket halfway with 5 gallons of freshly harvested, pure white vinegar.


  • Start by opening the hot and cold isolation valves on the water heater, and then turning on the pump in the 5-gallon bucket to circulate the vinegar through the heater.


  • Allow the pump to circulate for 45 minutes, then switch off the pump and allow the vinegar to drain from the water heater via the hoses into a pail (see illustration). Close the cold-water isolation valve to prevent ice formation.


  • Remove the vinegar from the bucket and insert the open-ended hose back into the bucket to complete the process. Turn on the cold-water supply valve and allow the water to run into the bucket for five minutes while the valve is open. Close the cold-water supply valve and detach the garden hoses from the inlet valves to prevent them from bursting.


  • Turn off the hot-water isolation valve if it is still on. Remove the inlet filter screen from the water heater according to the instructions in the owner’s handbook, then rinse the screen to remove any sediment. Reinstall the screen if necessary.


  • The hot-water supply valve should be turned on first, followed by the cold-water supply valve. Open a few of hot-water faucets throughout the home to bleed any air out of the hot-water pipes before starting the project. Once there is no more air in the lines, turn off the faucets.
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Ensure there are no leaks in the water heater’s connections by visually inspecting them. Turn on the gas supply valve, if the water heater is equipped with one, as well as the circuit breaker for it. Check to see whether there is hot water coming out of the faucets.

Things You Will Need

  • To make sure that there are no leaks in the water heater, inspect the connections. Install a circuit breaker for the water heater and activate the gas supply valve if it is fitted. Check to see whether the faucets are producing hot water.


  1. It is not recommended to cleanse the water heater without first shutting off the electricity and the gas (if it is a gas heater), as this might cause harm to the appliance. As a precaution, always open the unit and use a non-contact electrical tester to ensure that all power sources have been disconnected before proceeding with the system flushing. It is possible that the device will be damaged if all power sources are not turned off before flushing.

How do I flush clean my Rinnai tankless water heater? (R)

It is possible for a tankless water heater to collect mineral build-up over time, which can corrode the walls of the heating chamber within the tank. For regular maintenance and cleaning of your tankless water heater, it is necessary to rinse those mineral deposits out at least once a year using a hose. Follow this straightforward procedure to guarantee that your tankless water heater performs and operates at peak efficiency. Please take the time to go through all of the directions before starting, as you’ll want to ensure that you have all of the essential items on hand for the procedure.

Remove the tankless water heater’s power supply by following these steps: 1. 2. Turn off the main gas valve or the circuit breaker for any electrical equipment that are not in use. 3. Turn off (close) the three water valves that are connected to your tankless water heater. 4.

  • During the cleaning procedure, this stops cold water from entering the water heater and hot water from exiting the water heater. The water valves are comprised of three parts: a cold water valve (which is colored blue), a hot water valve (which is colored red), and a main valve, which is responsible for bringing water into your home.

4. Remove the purge port valve caps from the purge valves situated on each of the cold and hot water valves one at a time, taking care not to damage them.

  • The purge valves are distinguished by their little handles that mimic the letter “T.” In order to alleviate any pressure that has built up inside the valves and to avoid excessive hot water from pouring out during the cleaning process, this step must be carried out. Because there may be pressure when removing the purge port valve covers, it is critical to double-check that the hot water valve has been properly switched off for your safety. Make sure to handle each cap with care to ensure that the rubber sealing discs remain in place. These are required in order for your valves to operate correctly.

5. Connect a hosing line to each of the three valves in the system.

  • Tankless water heater hosing lines are available at any home improvement store that carries water heaters if the manufacturer did not include them with your tankless water heater. There must be adequate length between the water heater and the bucket for the hosing lines to be effective. Please refer to the tankless water heater manufacturer’s instruction manual, or contact the manufacturer directly if you require specific instructions on how to do this step. In certain situations, you may be required to utilize a sump pump and connect hoses in order to discharge and flush water from the tankless water heater’s cold and hot water valves during this operation.

6. Twist the purge port valves so that they are perpendicular to the positions of the cold and hot valves, and then close them. 7. To clean your tankless water heater, fill a 4-gallon (15.1-liter) bucket halfway with undiluted white vinegar. Never apply any type of chemical solution on your skin.

  • Given that the majority of your home’s drinking and bathing water is most likely routed through your tankless water heater, employing chemical cleaning solutions might be highly hazardous to your health.

8. To complete the flushing and draining operation, according to the directions provided in your manufacturer’s handbook. 9: When the flushing operation is finished, shut the purge port valves by twisting the T-shaped handles. 10. Disconnect and remove the hosing wires from each of the valves in the sequence listed. 11. Attach the purge port valve caps to the purge valves using the hose clamps.

  • Tighten the caps all the way down and securely. Take care not to overtighten or damage the rubber sealing discs that are contained within the caps, though.

12. Refer to your water heater’s owner’s handbook for specific advice on how to properly restart the unit.

  • If this is the case, you may need to rotate and open the cold and hot water valves so that they are parallel to one other and the main valve’s position.

Pick a sink tap within the house and turn on the hot water gently, allowing enough time for air to travel through the pipe.

  • Make sure to keep the water running until it flows consistently and there is no air escaping (you may recognize this by a slight sputtering sound). It might take up to 2 or 3 minutes for all of the air pockets to be expelled from the system.

How to Flush a Tankless Water Heater and Clean the Air Intake Filter

Water heaters that do not have tanks will accumulate calcium and debris on the heating components and filters within the unit. It’s critical to cleanse your system with food-grade white vinegar at least once every 12 to 18 months to keep it running smoothly. The performance and life of your water heater will be extended if you do this straightforward maintenance. This is also a good opportunity to remove and clean the air filter inside the tankless water heater while you’re conducting your regular cleaning.

However, this procedure may be used to any tankless water heater so long as you can identify the necessary components on your machine.

Step 1: Gather Your Materials

You should note that the knobs under your tankless water heater are color coded for your convenience. These levers are responsible for turning off the water and gas to your tankless water heater. If the levers are parallel to the pipe, it implies it is turned on, and if they are perpendicular, it means it is turned off. Make sure they are all perpendicular to the pipes before turning them on. As a result, the gas (yellow handle on the right side linked to the silver pipes), the central yellow handle, the cold water input (blue), and the hot water outflow will all be turned off (red).

Step 3: Unscrew the Cold Water Service Valve

A service valve is located just above the red and blue levers. The service valve can now be opened once the levers have been rotated such that they are perpendicular to the pipe and the water has been turned off to the tankless hot water heater. But first, gather your stuff and get ready to start. Please keep in mind that there is an external pump that is hooked to the wall near the ground level. The electronic components of the gadget are visible via the vents located at the top of the device.

  • Make sure you have a bucket ready to capture any excess water that may come out of the faucet.
  • Even though it is a small amount, you do not want it on your garage floor.
  • Make sure one end of the hose is inserted into the bucket so that when you remove the service valve cap, you may try to plug it into the opening fast and divert part of the water into the bucket.
  • Our water heater is only set to 120 degrees Fahrenheit, which I believe to be the case.
  • The water that comes out of the hot water service valve should not be too hot if you have been taking hot showers, using the dishwasher, and running the washing machine just before doing this.
  • If the water is hot, you may want to unscrew the service valve carefully so that you don’t burn yourself while doing so.
  • It occurred to me at that point that the water was not hot, but rather warm, so I completed unscrewing the service valve, plugged in the hose, and allowed the water to drain into a pail.

Take note that the hot water side of the faucet releases water considerably more quickly and in greater quantities than the cold water side.

Step 4: Setup Your Vinegar and Pump

The hoses you used to connect to the service valves in the previous step should be ready to use for this step by now assuming you did so in the previous step. Make sure you empty your 5-gallon bucket of any water that has accumulated in it from the service valves. Approximately 4 gallons of food-grade white vinegar should be added to the bucket. I purchased a generic brand from Safeway, and the total cost for four gallons was $16. Attach the line that connects to the cold water (blue) service valve to the sump pump’s top outlet.

  1. Do not connect the pump at this time.
  2. Because there is no on/off button, it will automatically turn on as soon as you connect it into a wall outlet.
  3. It is not necessary to screw it into the pump; instead, it should be put loosely in the vinegar bucket.
  4. Connect the pump to the electrical outlet as soon as possible.
  5. At the very least, you’ll keep it like way for at least 60 to 90 minutes.

Step 5: Cleaning the Air Intake Filter

Additionally, while the vinegar is being circulated, you should wipe out the air intake filter. If you’ve been noticing an error message on your screen that says “027,” you’re not alone. This indicates that you should clean the air intake filter. The tankless water heater’s air intake filter is situated within the tankless water heater. Don’t worry, it’s not difficult to get to, but you must first remove the tankless water heater face plate before you can get to it. A total of four screws hold it all together.

  • It is necessary to first remove all of the screws from the face plate before lifting upwards and releasing the hook that connects the top of the face plate to the top of the tankless water heater frame.
  • Then you’ll want to look for the single screw that holds the air intake filter in place.
  • As soon as you have unscrewed the one screw that holds the air filter, pull the whole thing slightly towards you and then slant it slightly so that it will slide over the motor, and you have successfully removed the air filter.
  • Afterwards, I just strolled over to my water spout outside my garage and ran it on full blast, thoroughly rinsing the filter.

Replacing the tankless water heater face plate and allowing the pump to continue to operate for the remaining 60-90 minutes is recommended. It is not necessary to plug the tankless water heater into an electrical outlet until after you have completed the flushing procedure.

Step 6: Rinse Your Tanless Water Heater After the Vinegar Treatment

Now that the vinegar has been pumped through the tankless water heater for 60-90 minutes, it’s time to rinse the vinegar out of the tankless water heater. Remove the sump pump from the wall outlet by unplugging it and lifting it out. Allow it to drip into a vinegar bucket and save it aside for later usage. I made the decision to put the vinegar into the toilet rather than on the grass or plants in order to prevent hurting the plants or grass. Now that you have a bucket that is empty, place the bucket back beneath the tankless water heater to keep it there.

  1. Replace the service valve cap with a screwdriver and tighten it.
  2. Allow around 4-5 litres of water to flow through the tankless water heater and out the hot water line into a bucket by releasing the lever controlling the cold water intake.
  3. After everything has been completed, it is necessary to inspect the water filters.
  4. These may be unscrewed with just your fingers if necessary.
  5. After removing the filters, make sure to thoroughly check the area for debris.

Step 7: Reattach Everything and Turn It on – Moment of Truth

Following the complete descalement and cleaning of your tankless water heater’s air intake filter, it is time to reassemble everything. Before opening any valves, double-check that all service caps are securely fastened. After you’ve made certain that everything is properly sealed, you may begin opening valves. I’d start with the cold water valve and work my way up from there. You’ll hear the sound of water streaming inside your body. After that, turn on the hot water faucet. After that, the gas and central circulation valves are opened (yellow).

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As soon as the display turns on and the machine begins to cycle, you may observe various symbols on the screen.

I hope everything goes as well for you as it did for me.

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Previous PostNext PostHot water at your fingertips! One of the advantages of installing a tankless water heater is that it saves space. Another advantage of a tank water heater is the potential for energy savings of up to 50% over a normal tank water heater. In the same way that any other household appliance performs more effectively with proper maintenance, your water heater will work more efficiently with proper care as well. The first step is to do routine maintenance! Read today’s post for six suggestions on how to clean a tankless water heater and perform other essential maintenance activities.

Maintaining your water heater on the interior as well as the outside can assist to guarantee that it operates at peak efficiency. You might even be able to extend its usable life!

1. How Often Should You Clean a Water Heater?

Whatever your experience level with tankless water heaters is, whether you’re a new convert or have had your unit for several years, you’ve probably had queries about how often you should clean the unit. The majority of water heater manufacturers recommend cleaning your water heater once a year. To be sure, the frequency may vary depending on your location and the quality of your drinking water. In the case of hard water, you may need to cleanse your water heater more frequently than in other circumstances.

Residents in all cities are provided with monthly or quarterly updates on the state of municipal water systems by city staff.

Concerning the cleaning of the unit’s outside, we’ll get to it in a minute.

2. Taking Care of Exterior Maintenance

The majority of homeowners take pleasure in performing at least a few house maintenance tasks themselves. In order to ease into water heater maintenance if you are new to the game, taking care of the outside of your water heater is a good first step. Exterior upkeep does not necessitate the expenditure of a significant amount of time or resources. Begin by wiping down the cover of the book. Using a non-abrasive cleanser and a soft cloth to clean the device helps to maintain it clear of dust and avoid the formation of rust.

  1. Checking pipes during cold weather is important for our northern neighbors to avoid frozen pipes.
  2. Finally, if your tankless water heater is equipped with a pressure release valve, you should make sure it is working properly.
  3. If you have any questions concerning your water heater, you should consult with a plumber.
  4. The process of flushing the water heater will take a bit more time.

3. Why You Should Flush

Water heaters, like other appliances, accumulate limescale deposits over time. Failure to descale conventional tank models can result in an explosion in some instances. Tankless water heaters will not explode, but if the sediment is not flushed out of the unit, it may cause the heat exchanger to work harder than it needs to, increasing the risk of failure. The ability to keep sediment washed out not only allows the water heater to operate more effectively, but it can also assist prevent additional issues.

Consider an isolation valve to be similar to the shut-off valve on a normal tank water heater in terms of function.

It is possible that your water heater does not have an isolation valve. If it doesn’t, you might want to consider having a plumber install one. When doing maintenance, the absence of an isolation valve might pose a serious safety threat.

4. What Supplies Do You Need to Clean the Water Heater?

We’ve covered safety; now it’s time to speak about the supplies you’ll need to flush the unit. These are the materials you’ll need: While you may purchase each component separately, a flush kit contains everything you need in one convenient package. Alternatively, you may use 4 gallons of undiluted white vinegar instead of the descaling solution included in the flushing package.

5. How to Descale a Tankless Water Heater

We’re presenting the simple methods for descaling a water heater since it’s one of the maintenance activities that many homeowners can complete with little or no help from a professional. The first step is to turn off the power that is feeding your water heater. Locate and close the gas isolation valve if one exists. Shut off the hot and cold water shut-off valves while you’re working on the unit to prevent water from entering the unit. If your machine is equipped with a pressure relief valve, carefully open it to relieve any built-up pressure.

  • Next, put the submersible pump in the bucket you just made.
  • You may either pour four gallons of vinegar into the bucket or use the descaler that came with the flush package to remove the scale.
  • Allow at least an hour for the descaling solution of your choice to circulate through the hot water heater.
  • Following completion of descaling, switch off the pump.

6. Final Steps for Tankless Water Heater Cleaning

Closing the cold water service port and opening the cold water shut-off valve are the next tasks you need to do. This step removes any vinegar that may have remained. Following that, you’ll close the valve and allow the water to drain completely. It is now necessary to shut the hot water port. Finally, if there is a cold water input filter, make sure to remove it as well as the hot water in-line filter before continuing. Flush both of them in the sink to ensure that any remaining sediment is removed.

Keep in mind that, while it might be a fun DIY project, you may feel more comfortable having a professional plumber complete the task.

Need to Schedule Tankless Water Heater Maintenance?

Maintenance, including tankless water heater cleaning, should be performed at least once a year to ensure that everything is running well. You may need to perform additional duties, such as cleaning off the unit’s outside, on a more frequent basis, especially if the location where the water heater is installed receives a lot of dust. While you can perform some simple maintenance on your own, why not enlist the assistance of our team?

For both tankless and traditional tank water heaters, we are delighted to plan periodic descaling and yearly service appointments with you. For a free estimate, please contact us immediately. Previous PostNext Post Previous Post

How to flush your tankless water heater and save $$$!

Despite the fact that tankless water heaters are efficient and effective, they require regular maintenance to guarantee that scale does not build up in the system. Flushing your tankless heater is a straightforward process that should take no more than 1-2 hours to complete. Accomplish this activity once a year is sufficient for the majority of water quality issues, but if you have really hard water, you may want to complete it more frequently.

Step by step

Tankless hot water heaters are a wonderful technology that not only are more energy efficient than their tank-based counterparts, but they also give customers with a limitless supply of hot water. Every year, much like traditional tank hot water heaters, tankless hot water heaters require flushing to guarantee that they operate at peak efficiency. Failure to flush your tankless hot water heater may result in the formation of scale, which are hard mineral deposits, inside the device, which will reduce its efficiency.

  • It is possible to avoid long-term difficulties by doing easy annual maintenance!
  • First, check to see if you have flush valves installed; if you don’t, you’ll need to hire a plumber to do so before you can continue.
  • Let’s get this party started!
  • For additional information on building science and exquisite craftsmanship, make sure to subscribe to Matt’s YouTube Channel.
  1. Check for Flush Valves if there are any. Check to see if your unit is equipped with a set of flush valves. These will be similar in appearance to a hose bib and will feature screw-on caps. Please install these first if they are not already installed on your computer before continuing. In order to complete this work properly, we recommend that you engage a professional plumber. Shut off the gas or electricity supply. By utilizing the inline valve, you may turn off the gas supply to the machine. Utilize the disconnect or breaker if you have an electric item
  2. Otherwise, use the fuse. Turn off the water supply. Open the Flush Valves if necessary. Shut down all of the cold and hot water valves that come into and out of the unit. Once this is completed, remove the caps and open the flush valves. Ensure that the filter is clean. If necessary, remove and clean the inline filter. This will be situated just above the cold-water intake pipework. Remove the detachable filter and clean it by swishing it around in with vinegar, followed by some water, before reinstalling. System of flushing
  3. Make the Vinegar according per package directions. Submerge the Pump in water. Connect the hoses together. Fill your 5-gallon bucket halfway with ordinary white vinegar (three gallons). Submerge your pump and connect the hoses that run from the pump to the flush valves on the side of the tank. Make certain that your pump is only turned on while it is immersed, or it may overheat. Run the pump for a total of 90 minutes. Turn on the pump and let the vinegar to circulate throughout the system for 90 minutes. The mild acidity of the vinegar is what causes the scale to break down on the inside of the pump
  4. Turn off the pump. Disconnect the hoses from the boiler. Pump should be turned off and hoses should be disconnected after 90 minutes. Fill up the spaces between the flush valve covers and close the flush valves. Double Take a look at the Filter Check the filter once again to ensure that it is free of obstructions. Restore the flow of water, gas, or electricity. Open the cold and hot water valves on your faucets. Re-open the gas valve or re-energize the electric system. Due to the fact that gas tankless hot water heaters do not have a pilot light, there is no need to be concerned about re-igniting anything. Complete the form. All done and you have plenty of hot water accessible from your clean and clear heater to last you another year. Finished! Don’t forget to mark this activity as completed on your dashboard after you are finished.

How to Flush a Tankless Water Heater: Gas and Electric

Flushing a tankless water heater on a regular basis is the single most critical action you can conduct to ensure that your heater is operating at top efficiency. It is possible that failing to flush your tankless system can result in a shortened service life as well as increased fuel expenditures. Though it is strongly recommended that you have a professional inspect your unit on an annual basis, the flushing operation is not too difficult and might save you money if you complete it yourself.

Knowing what has to be done, whether you intend to handle it yourself or hire an expert, will help you get the most out of your tankless water heater.

Preparing to Flush Your Tankless Water Heater

To ensure that your tankless water heater continues to operate at full performance, it’s crucial to do regular maintenance on it.

However, before you can begin, you’ll need to gather all of the necessary tools. In addition, you’ll want to put safety at the forefront of your thoughts. Here are a few safety concerns to keep in mind:

  • When working with your tankless water heater, you should use extreme caution at all times. The water within the system can be quite hot, especially if the heater was just turned on
  • We highly advise against flushing your tankless water heater with chemicals. A natural cleaning product that is both safe and effective, vinegar also has a low environmental impact. Always refer to your tankless water heater’s owner’s handbook for exact installation instructions for your particular model.

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Necessary Supplies

Flushing is required on a regular basis for both gas and electric tankless water heaters. It is crucial to note that the methods for each kind of tankless water heater are completely different. Electric systems are simple to flush, and in most cases (apart from the vinegar), you will just want a screw driver and a wrench, which you most likely already have on hand. Gas distribution systems are more complicated. The following is a list of the items that are often required to flush limescale from gas tankless water heaters: Some manufacturers include Isolation Valves with Service Ports with their gas tankless water heaters, which may be found here.

  1. Isolation Valves with Service Ports are highly recommended if your gas tankless heating system does not already have them.
  2. They are a good purchase that you will not be disappointed with.
  3. Flushing techniques for electric heating systems are completely different from those used for gas heating systems.
  4. Isolation valves make cleansing a gas tankless water heater considerably easier than it would otherwise be.
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Deliming Solution

There are various commercial solution solutions available that may be used to remove lime scale build-up; however, most manufacturers advocate using vinegar instead of these products. It’s safe, it’s ecologically friendly, it’s cheap, and it’s quite effective. Tankless water heater repair may be performed for as little as the cost of a few gallons of vinegar if you have all of the essential equipment and supplies on hand. Find a Local PlumberToday is the day to fix your plumbing emergency!

How to Flush aGasTankless Water Heater

The flushing processes outlined below are for tankless water heaters that are powered by natural gas. If you have an electric tankless water heater, please refer to the instructions for electric tankless water heaters for further information. As is always the case, your greatest source of information is your owner’s handbook, which will provide instructions particular to your tankless system. The techniques outlined here should only be used as a guide, not as a set of absolutes. The amount of time advised for the vinegar to circulate varies from maker to manufacturer, but as a general rule of thumb, the longer the period, the better.

For those who do not have have them installed, we recommend that you call a competent professional to either install them for you or flush your tankless system.

Flushing Procedures for Gas Tankless Water Heaters

  1. The electrical power to the tankless water heater should be turned off
  2. Removing the access panel and using a non-contact voltage tester to check the wires flowing into the terminal to ensure that all power has been unplugged is recommended. DISCONNECT THE HOT AND COLD VENTILATION VAULTS. As a result, cold water will be prevented from entering your unit and water will be prevented from entering your home’s plumbing system
  3. Open the Hot Water Pressure Relief Valve located on the Hot Water Line to relieve the pressure buildup. Use cautious since any water that is discharged may be extremely hot
  4. The cold water service port on one end of Hose1 should be connected to a Submersible Pump on the other end of Hose1. Connect one end of Hose2 to theHot Water Service Port and the other end to the Submersible Pump in a 5-gallon bucket. Into the bucket, insert the end of Hose2 that is not attached. Pour 4 gallons of virgin, food-grade white vinegar into the 5-gallon bucket that holds the submersible pump (see illustration). DON’T dilute the vinegar in any way. Allow for at least 60 minutes of circulation of vinegar through the tankless water heater by opening the hot and cold service ports, turning on the submersible pump, and allowing the vinegar to flow through the tankless water heater. The lime scale build-up will be broken down and flushed away as a result of this procedure. This should be done at a pace of 4 gallons per minute
  5. If your pump circulates at a slower rate, you should let the pump to run for a longer period of time. Immediately turn off the Submersible Pump and dispose of the vinegar.

Rinse the Vinegar from the Tankless after Flushing

  1. Remove the unattached end of Hose2 from the bucket and dispose of it in a drain or on the street
  2. HOSE1 should be removed and theCold Water Service Port should be closed, followed by the Cold Water Shut-off Valve being opened. Ensure that you do not open the hot water shut-off valve. As soon as theCold Water Service Valveis turned on, fresh water will begin to flow through the device, flushing away any vinegar that may have remained. Allow the water to flow for 10 minutes before closing the Cold Water Shut-off Valve to prevent the water from freezing. As a result, the water will no longer flow through the device. Take out Hose 2 and close the Hot Water Service Port after the water has stopped draining.

Clean the Inlet Filter

  1. Remove the Cold Water Inlet Filter from the system. (A Cold Water Inlet Filter is included with every tankless water heater.) A few manufacturers additionally include a Hot Water In-Line Filter, which should be cleaned at the same time as the rest of the system.)
  2. Remove any sedimjavascript:void(0)ent that has accumulated within the housing and screen of theCold Water Inlet Filter by flushing it with tap water. Replace theCold Water Inlet Filter in a secure manner, and then OPEN theCold Water Shut-off Valve. Repair or replace the access panel cover, then re-energize the unit’s electrical power supply

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It is recommended that you follow the flushing methods outlined below for electric tankless water heaters. For those of you who have a gas tankless water heater, please refer to the guidelines mentioned above, which are particular to gas tankless water heaters. These processes should only be used as a reference; as is always the case, your tankless water heater’s owner’s handbook will be the most reliable source of information for your particular tankless water heater. Please see this page for further information on why it is vital to consult your owner’s manual.

The maintenance requirements for electric tankless water heaters are lower than those for gas heating systems; nonetheless, they still require periodic maintenance and inspection.

The majority of manufacturers recommend flushing once a year, although it should be noted that the frequency of flushing is ultimately controlled by the hardness of your water.

More frequently you should flush your toilet, the harder the water is. Emergency Plumbing – 24 Hour ServiceRepair – Install – Replace Emergency Plumbing – 24 Hour Service


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Flushing Procedures for Electric Tankless Water Heaters

  1. The electrical power to the tankless unit should be turned off at the circuit breaker
  2. SHUT OFF THE COLD WATER VENTILATION VALVE. As a result, water will not be allowed to enter the tankless system
  3. By opening the taps in your house, you may drain the water from the tankless water heater. Close the hot water shut-off valve if it is not already closed. Removing the lid and using a non-contact voltage tester to double-check that no electricity is reaching the device is recommended.

Remove the Electrical Heating Elements

  1. Removing the screws that hold the wires that are attached to the top of the heating elements is necessary. To release the hexagon brass top of the heating element, use a wrench to turn it clockwise. Remove the heating element from the copper tank by rotating it in the counter-clockwise direction. Inspect the heating components for wear and tear. If any of them are cracked, they should be replaced immediately. Placing the heating components within the copper chambers of the tankless unit is the best option.

Fill Copper Chambers with Vinegar

  1. Virgin, food-grade white vinegar should be used to fill the copper chambers (which contain the heating components). Leaving the vinegar to soak in the chambers for 90 to 120 minutes is recommended
  2. After draining the vinegar, replace the heating components with new ones that are tightened in a clockwise rotation. The cables should be secured to the top of the heating elements by using a screwdriver.

Flush the Vinegar from the Tankless

  1. RELAX and allow water to flow into the tankless system by opening theCold Water Shut-off Valve. Keep an eye out for leaks as the tank is full. Open the Hot Water Shut-off Valve if necessary. INSTALL a number of hot water faucets throughout your home and leave them running for approximately 5 minutes. This will aid in flushing out the vinegar and removing any air pockets that may have formed inside the hot water pipes.

Clean the Inlet Filter

  1. The Cold Water Inlet Filter should be removed from the cold water line. Remove any silt and debris from the filter housing by flushing it with water
  2. Reinstall the filter with care.

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Importance of Checking your Owner’s Manual

When purchasing an electric tankless water heater, it is crucial to read the owner’s handbook carefully because there might be major design variances between manufacturers. When a tankless unit is not properly flushed, it is more likely to be damaged and require servicing or repair. A number of manufacturers, such as EcoSmart, provide the option of installing Isolation Valves with Service Ports, which allow the user to flush the system in the same manner as you would a gas tankless water heater.

  • Several other manufacturers, including Bosch, employ a design that has narrower water flow channels and requires a whole new technique of cleansing the system.
  • If this occurs, professional repair will almost certainly be required.
  • The electrical heating elements should be removed and soaked in vinegar for 60-90 minutes, according to their flushing recommendations.
  • The canister can then be closed and sealed when the replacement O-ring has been inserted in its proper position.

How Often Should a Tankless Water Heater Be Flushed?

Flushing a tankless water heater is an important element of ensuring that the system continues to work at its peak performance. Although manufacturer guidelines differ, the majority of them recommend that you cleanse your tankless system once every 12 months. Tankless water heaters are fundamentally different from their tank-style counterparts; nonetheless, both are adversely affected by limescale build-up in the water supply. Tankless systems will not spring a leak if preventative maintenance is not performed, but they will develop extremely serious problems that may be both expensive and inconvenient if not addressed immediately.

Impact of Hard Water

When it comes to the suggested flushing frequency, the hardness of your water supply is usually the most important factor to consider. Water hardness relates to the amount of minerals present in the water, and certain places are more prone to hard water than others. Learn how to keep your tankless water heater safe from hard water. Put another way, when the water has a high mineral content, your tankless heater will experience increased lime scale build-up within the device. If you reside in a region with high amounts of hard water, this is unfortunately the way things are, and you’ll want to take preventative measures to avoid problems in the future.

Tankless water heaters transmit heat to the water through the use of a heat exchanger.

Heat exchangers are extremely sensitive to lime scale buildup, and even a tiny quantity of accumulation can have a severe influence on the performance and efficiency of a tankless heater. Find Local Plumbing Professionals

Damaging Effects of Lime Scale Build-up

It is inevitable that the quantity of lime scale build-up in your tankless system will rise over time, and as more and more build-up occurs, the number of burner cycles in the heat exchanger will increase as well, in order to compensate for the efficiency that is lost. The increase in the number of burner cycles necessitates the tankless system working harder than it should in order to get the same outcomes as previously. Along with decreasing the efficiency of the heater, this will have a detrimental influence on the service life of the heat exchanger and, as a result, on the tankless water heater’s overall performance.

It’s also important to be proactive when it comes to cleaning your tankless water heater since lime scale build-up may wreak havoc on your tankless water heater, causing damage, loss of efficiency, and limited service life.

Diagnostic codes are frequently shown on higher-end systems to notify the homeowner when the limescale build-up has reached a point where it is no longer possible to operate the system.

Keeping Your Tankless Water Heater Healthy

We strongly recommend that you read our other articles on how to care for your tankless water heater, even though this one dealt especially with flushing a tankless water heater. A tankless water heating system may have a service life of up to 25 years if it is maintained properly, and it can save you money on your electricity bills every month. The following articles will assist you in getting the most out of your tankless heater:

  • Keep your tankless water heater operating at peak performance by following these steps: Hard water can cause damage to your tankless water heater. Here’s how to protect it. Why Your Tankless Water Heater Needs a Sediment Filter
  • Why Your Tankless Water Heater Needs a Sediment Filter

In the event that you are a first-time tankless water heater owner, you may want to consider hiring a professional to cleanse your system the first time around. You will have the opportunity to observe, ask questions, and make notes. It will be money well spent, and you will have the satisfaction of knowing that you will know exactly how to accomplish the responsibilities in the future as a result of your training. Repair and Installation of Water Heaters at the Lowest Possible Price Now is the time to call!

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