Flushing the tankless water heater
Flushing the tankless water heater is a simple maintenance procedure. Perform as often as the manufacturer recommends. More often as the conditions determine.
What determines when the tankless water heater needs to be flushed?
Time, temperature and water hardness determine when your system should be flushed. Read the recommendation of your tankless manufacturer for a time-based interval. Also, note the hotter you run your water temperature the quicker it builds upscale. The biggie, water hardness, if your having problems with water scale build up on all your water faucets, showers, sinks you may want to accelerate the schedule to twice a year.
My tankless service valves
Flushing the tankless water heater procedure
- Turn off the electrical power to the water heater. My water heater plugs into a wall outlet. I remove the plug from the outlet. An external display verifies that power is on. If your unit is hard-wired you may have to go to the circuit breaker box of your home and flip the correct circuit breaker to disconnect the power. Either way, always verify that no power exists when working on your system.
- Turn off the gas to the water heater. If there is a gas shutoff valve it should be close to the water heater.
- Disconnect the water heater from the cold water supply. Turn the service valve handles to disconnect the water heater. The house will have cold water while the water heater is being flushed. My valves also have additional shut off valves for the hose connections. This allows me to connect the hoses after the water heater has been disconnected from the cold water supply system without spilling water all over the floor. Then I can open the valves to the hoses and drain the tank heater in preparation for flushing.
- Connect one end of a washing machine hose to the outlet of the sump pump, then connect the other end of the hose to the inlet service valve. Connect a second washing machine hose to the hot water side(outlet) service valve.
- Place the pump and the open end of the hose into a 5-gallon bucket. Elevate the pump in the bucket to prevent sucking up fines from the bottom of the bucket. Fill the bucket with 3-4 gallons of fresh, clean white vinegar.
White Vinegar
Cider Vinegar or White Vinegar?
- Turn on the pump in the bucket to start circulating the vinegar through the water heater. Verify that the pump is pumping the vinegar by checking the return line for flow. Check the return water hose flow every 20 minutes. It is normal for the vinegar to get hot. Let the pump run for 45-60 minutes then turn off the pump. Lift the return line so it is higher than the valves and let the vinegar drain from the water heater through the hoses and back into the bucket.
- Dump the vinegar out of the bucket. Fill it with clean water in preparation for flushing any remaining vinegar in the water heater, hoses, and pump.
- Place the return hose and the pump back into the bucket. Turn on the pump and let the water flow for a few minutes. Turn off the pump. Lift the return hose above the valves and let the water drain into the bucket. Close the hose valves and disconnect the washing machine hoses from the inlet valves. Replace the caps on the valves.
After the flush, purge the air
- Remove the inlet filter screen per your owner’s manual and clean the screen to remove any sediment. Reinstall the screen and turn on the cold water(inlet) supply valve first. Then turn on the hot water(outlet) supply valve.
- Open the nearest hot water faucet to the water heater to bleed any air from the hot-water line. Close the faucet when no more air is in the line.
- Check the water heater’s connections to make sure there are no leaks. Turn on the gas valve, and reconnect the power to the water heater. Check for hot water at the nearest faucet.
Do you need a tankless water heater kit? Want to make your own kit?
Related Article: Tankless Water Heater Flush Kit
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Trained in the mechanical arts. I have worked on anything dealing with a home from changing a light bulb to moving a load bearing wall. As for the recipes, they came about after I could not find what I was looking for and recipes that over a lifetime I have come to love and want to share with the world.
Latest posts by RayC. (see all)
How many hp should the pump be?
I don’t think horsepower is all that important in this case. It comes down to the gallonage that it can pump. If the pump had a lower gallonage per minute rate I would have simply increased my time for recirculating the vinegar. My hoses are 6 feet long and the rise is approximately four feet. So the pumps head is not that great. In my case my pump is a 1/6 hp pump simply because that was the pump with the best price for the gallonage it could pump. Sorry for the lateness of this reply my computer was having problems. I hope this helps. If your thinking about making a flush kit here’s what’s important and what equipment you will need.