Tankless Water-Heater Maintenance
A little cleaning can help tankless water heaters perform like new.
To function efficiently, a tankless water heater requires periodic maintenance. Here are three easy-to-accomplish tasks.
Clean the air filter
Turn off and unplug the unit, then remove the front cover. Locate the air filter and remove it. A dirty filter can reduce performance, so give it a good look. If necessary, clean it using a soft-bristled brush and a mild solution of dish soap and water. Rinse it with clean water, dry with a lint-free towel, and reinstall.
Clean the in-line water filter
Locate the in-line water filter at the cold-water inlet. A clogged water filter also can diminish the heater’s performance. Before removing the filter, close the cold-water supply valve to turn off the water supply to the unit. Clean the filter by tapping it, running it under water, or wiping it with a cotton swab. Reinstall the filter, and reopen the cold-water supply valve.
Flush the unit
Mineral deposits from hard water also can reduce a tankless water heater’s performance. Clearing out these deposits is a little more involved.
- Begin by unplugging the water heater and closing the shutoff valves on both the hot- and cold-water lines.
- Connect a hose from the outlet of a circulation pump to the cold-water service valve, and connect a drain hose to the hot-water service valve.
- Pour 4 gal. of undiluted food-grade white vinegar into a clean 5-gal. bucket, and place both the drain hose from the hot-water service valve and the pump supply hose (connected to the pump’s inlet) into the vinegar.
- Open the service valves on both the hot- and cold-water lines.
- Turn on the pump, and allow the vinegar to circulate through the system at a rate of 4 gal. per minute.
- After at least an hour, flush the system with cold water to remove the vinegar and any loose minerals.
- Remove the free end of the drain hose from the bucket, and run it either to a drain or outside.
- Close the cold-water service valve, open the cold-water supply valve, and allow water to flow through the heater for five minutes.
- Afterward, close the cold-water supply valve, and clean the in-line water filter at the cold-water inlet on the heater to remove any loose deposits the filter picked up during the process.
- Clean the filter by tapping, running under water, or wiping with a cotton swab.
- Once clean, replace the filter.
- Close the hot-water service valve, and open both the cold- and hot-water supply valves.
- Disconnect all of the hoses, plug the unit back in, and power it on.
Before doing these or any maintenance protocols, check your make and model for specific requirements.
The flushing information is great - but for it to have value we need to have a better idea of how often this must be done for areas with high, normal, and low mineral content in the water.
Hi Albany_Chris — It's hard to say how frequently you need to flush the system. Typically you'll notice if/when the hot water pressure starts to drop, which is often a sign of mineralization gumming up the works. This may never happen with treated water or water that's naturally low in minerals. In areas with really hard, untreated water, you may need to flush it more than once a year to maintain performance. Generally, I'd say stick with manufacturer recommendations on frequency of maintenance unless/until you notice a drop in performance. If you notice performance dropping off more quickly than the recommended maintenance intervals, bump up the frequency of maintenance.
This is a bit oversimplified. For a more comprehensive video, including a source for the circulation pump, Google "Risinger, tankless maintenance."
Honestly, water heaters are quite complicated, but this information seems to be helpful!