How to maintain a tankless water heater

If you’ve ever enjoyed a long, hot shower without the fear of running out of hot water, you might have a tankless water heater to thank. 

These handy devices offer endless hot water, improved energy efficiency, and a space-saving design. But, like any appliance, they need regular maintenance to keep them running smoothly and extend their lifespan.

Mineral buildup and sediment can accumulate inside the unit over time, leading to reduced efficiency, increased energy consumption, and premature failure. Regular maintenance can prevent these issues, saving you money and extending the life of your water heater.

Here’s a simple overview of how to keep your tankless water heater in good condition.

Regularly Flush Your Unit

Flushing a tankless water heater involves the following:

  1. Shutting off the water and power supply (gas or electric)
  2. Attaching hoses to the flush valves and running a cleaning solution through the system
  3. Reconnecting everything 


  • ⬥ Check your manual and follow the instructions provided. 
  • ⬥ Consider hiring a professional if you’re uncomfortable with the task. Make sure you hire a pro who knows about tankless water heater systems.

Clean the Air Intake Filter

Most tankless water heaters have an air intake filter that traps dust, debris, and insects before they enter the unit. A clogged air filter can reduce efficiency and lead to performance issues. 

Here’s how to clean it:

  1. Turn off the power and water supply for safety.
  2. Follow the process described in your user manual for locating and removing the filter.
  3. Clean the filter. A vacuum with a soft brush attachment will make it easy to remove dust and debris. Or, rinse the filter with clean water and let it dry before reinstalling.

Inlet Water Filter

The inlet water filter is located on the tankless water heater’s cold water inlet pipe. It traps sediment, debris, and minerals from the incoming water supply. 

This helps protect the heater’s internal components from clogging and potential damage.

Checking and cleaning the inlet water filter of your tankless water heater is a relatively simple process that can help maintain efficiency and performance. 

Here’s a simple breakdown of the steps involved:

  1. Find the shutoff valves and turn off the power and water supplies that connect to the tankless water heater, or, if necessary, turn off the unit.
  2. Check the user manual to locate the inlet water filter location. 
  3. The filter housing might be screw-on or require pliers to loosen a retaining clip.  Consult your manual for specific instructions on how to remove the filter.

Cleaning the Filter

  1. Once removed, rinse the filter with clean water to remove any trapped debris or sediment. You can also gently brush away stubborn particles. 
  2. Avoid using harsh chemicals or abrasive tools that could damage the filter screen.
  3. Next, reinstall the filter and then turn the water back on. Slowly open the isolated cold water shutoff valve first, then the main house shutoff valve (if you closed it). After turning on the water supply, check for any leaks around the filter housing.
  4. Finally, turn on the power source (gas or electric).

Inspect and Clean the Condensate Drain

The condensate drain in your tankless water heater helps eliminate the acidic byproducts produced during the heating process. This is a drain line that removes condensation produced during the water heating process. 

As the cold water enters the tankless heater and gets heated up, moisture condenses out of the air. This condensate needs to be drained away to prevent buildup and potential mold growth.

Keeping this drain clear is essential to prevent clogs and potential damage to your unit. 

  1. To inspect and clean the condensate drain, start by locating it—it is usually found at the bottom of the unit. 
  2. Use a brush or compressed air to clear any obstructions or buildup. 

Regular inspection and cleaning, ideally once a year or as needed, will ensure your water heater continues functioning efficiently and avoid costly repairs.

Cleaning the Exhaust Vent:

The exhaust vent carries away combustion gasses from the water heater. For proper ventilation and safe operation, keep the vent clear of obstructions.

Usually, this isn’t a DIY job. The complexity and potential safety hazards are better left to a qualified technician. 

That said, you can visually inspect the exterior vent for any visible debris, such as leaves, twigs, or bird nests. If there’s a blockage, you might be able to remove it carefully from the outside. 

However, it’s recommended that a qualified technician clean the internal flue passage of the exhaust vent periodically according to the manufacturer’s recommendations. They have the proper tools and expertise to ensure safe and thorough cleaning.

Recommended Maintenance Frequency

The recommended frequency for checking and cleaning the inlet water filter can vary depending on your water quality.  Your user manual should provide guidance.  

Generally, it’s a good idea to check it at least once a year or more often if you have hard water or experience reduced water flow.

 Schedule Professional Maintenance:

Finally, if you’re uncomfortable or unfamiliar with maintaining your tankless water heater, don’t worry. It’s best to have a licensed technician inspect and service it periodically (e.g., annually or as per the manufacturer’s guidelines). They have the expertise to ensure your heater is in top condition.

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