Tankless Water Heater Maintenance: How To Guide

Tankless Water Heater Maintenance: How To Guide

Generally, Tankless water heaters are expected to have an average life-span of 20 years. However, to ensure that your heater gets 2 decades of use and serve you at optimum capacity, you must ensure that you carry out regular maintenance on it.

Water typically contains dissolved minerals which may begin to accumulate inside the heating chamber of your water heater with time. This can lead to damage to the heating surface. Purging your heater occasionally is recommended to prevent corrosion. The routine maintenance is something you can do entirely on your own. Here is a simple 7-step guide on how to maintain your tankless water heater.

What you need:

  • Hosing lines
  • Vinegar (about 3 liters will do)
  • The User manual for your heater
  • You might need tools to turn the valves if they have become too stiff but in most cases, this is rarely needed.

Step 1: Turn off the power and close off the water valves

When dealing with any household appliance safety is of utmost importance. The very first thing to do before you begin maintenance is to turn off the power supply to the water heater. The rule is the same whether you are using a gas powered unit or an electric one.

To avoid making a mess, you should also close off the water valves that supply cold water to your heater as well as the one that takes hot water out of it. In many homes, you might find a third pipe which is the one that brings water into your home. Close off all the valves to these pipes before you start the maintenance process.

Step 2: Remove the cap to the purge valves

Locate the valve caps for the hot water and cold water valves and remove it. Before you remove this cap, you should ensure that the valve is closed completely first. This will ensure that the pressure within the heater is relieved completely first. Failure to do this might be dangerous. Once you are sure that the valve is closed, you can proceed to remove the valve cap. Be sure to keep them in a separate place that is clean and dry as you will have to return them when your work is done.

Step 3: Attach hosing lines to the 3 valves on your unit

Most tankless water heaters come with their own hosing line. You should find it in along with the product package. However, if yours doesn’t, you will have to purchase a new one. Visit any local hardware store or online to get a hosing line. Be sure to pick one that is compatible with your unit. A detailed guide for attaching the housing line to your unit is always included in the user manual.

 Step 4: Open the purge port valves and purge the unit

Turn the purge port valves to a position perpendicular to the cold and hot water valves to open it.

Step 5: Clean your water heater

The next step is to clean up your unit. Do not use chemical cleaners for this as some might remain in the heater and get into your water. This may render it unsafe to use. Instead, experts recommend that you use about 3 gallons of vinegar in order to get the unit properly cleaned up. Once you have run the vinegar through, flush and drain the heater according to the instructions in your user manual.

Step 6: Close the purge port valves and replace the cap

This shouldn’t take you much time to do, quickly run through the step and your heater is back functioning properly.  

Step 7: Restart your unit

With all of these done, you can proceed to restart your unit and test if it has been perfectly fitted back together. The restart process varies slightly for a gas-powered heater and electric unit.


Regular maintenance is important to keep your tankless water heater unit in good condition. Most homeowners do this one in a year. The frequency of maintenance required will also vary based on where you live. If your water is hard, you should purge your heater more frequently since the rate of mineral buildup will be higher. Speak to an expert for more instructions if you are still unclear about the maintenance procedure for your heater.


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