How to Maintain a Tankless Water Heater

Tankless water heaters are a popular choice for homeowners who want hot water on demand, greater energy efficiency, and a compact design. But like any appliance, they need regular maintenance to work their best. With just a little upkeep, you can extend the life of your unit and avoid costly repairs.

Here’s a simple guide on how to maintain a tankless water heater to help you keep your home’s system running smoothly.

 

Flush the System Annually

Over time, minerals from your water—especially if you have hard water—can build up inside your water heater. This buildup can reduce efficiency, damage internal parts, and shorten the lifespan of your unit.

Flushing your tankless water heater once a year (or more frequently if you have very hard water) helps remove these mineral deposits. To flush your water, follow these steps:

1. Turn off the power and water: Shut off the gas line, or if your unit is electric, trip the circuit breaker. Then, use the nearby shut-off valve to turn off the water supply.
2. Release pressure: Carefully open the pressure release valve to relieve any built-up pressure in the system.
3. Remove the cover: Use a screwdriver to remove the access panel or cover so you can access the internal components.
4. Set up your flush system: Attach a hose to the cold water inlet. Connect the other end to a small sump pump or a flushing kit, then submerge the pump in a bucket filled with at least three gallons of distilled white vinegar.
5. Flush with vinegar: Turn on the sump pump and allow the vinegar to circulate through the system for one hour. This will break down limescale and mineral deposits.
6. Rinse with clean water: After an hour, dump the vinegar and replace it with clean water. Run the pump for another 10 minutes to flush out any remaining vinegar.
7. Clean up: Shut off the pump, disconnect the hoses, and flush them with clean water. Reassemble the unit by putting the cover back on.
8. Restart your unit: Follow your manufacturer’s instructions to properly restart your tankless water heater.

If you’re struggling with flushing your system or can’t access certain elements of your water heater, call a professional plumber for help.

 

Clean the Filters

Most tankless water heaters have two types of filters: an air filter and a water inlet filter. Both of the filters need to be regularly checked and cleaned or replaced in order to keep your water heater running smoothly.

Your water heater’s air filter is key in maintaining proper ventilation. A clogged or defective air filter can place strain on your system and cause it to use more energy. Regularly check this filter and replace it whenever necessary.

Your tankless water heater has inlet filters that catch sediment and debris from your water supply. If these filters get clogged, your unit may lose water pressure or shut down altogether.

To clean these filters:

• Turn off the water and power to your unit.
• Locate the inlet screen filter (usually near the cold water intake).
• Remove it and rinse thoroughly under running water.
• Reinstall the filter before turning the system back on.

Be sure to check all of these filters every 6-12 months, depending on your water quality. If you have hard water, it is recommended to check your inlet filters more frequently.

 

Test & Adjust the Temperature & Pressure

Your water heater’s temperature should ideally be set around 120°F (49°C). This is hot enough for most uses but helps prevent scalding and reduces energy use. You should also check the water pressure—too much pressure can strain your system and cause leaks.

Use a pressure gauge to make sure your home’s water pressure is between 40–60 psi. If it’s higher, adjust the pressure relief valve.

 

Descale the Unit

Even with regular flushing, lime and scale can still form inside your system, especially in areas with hard water. Descaling involves circulating a descaling solution (like vinegar or a commercial descaler) through the unit to break down and remove mineral deposits.

Descaling should be done at least once a year or more frequently in hard water areas. This helps maintain energy efficiency and protects the heat exchanger from damage. Descaling can be tricky to do without the proper experience. Connect with local plumbing professionals to ensure it’s done right and doesn’t cause further damage to your system.

 

Schedule Regular Professional Maintenance

While many maintenance tasks can be DIY, it’s a good idea to have a professional at least inspect—if not regularly maintain—your tankless water heater annually. From inspecting your gas and electric connections to looking for leaks or signs of corrosion, professional maintenance can catch small issues before they become big problems—saving you money and giving you peace of mind.