Why You Should Descale A Tankless Water Heater

Written on: April 13, 2021

If you get your water from a well or from a local municipal water supply here in Pennsylvania, chances are it contains a fair amount of minerals (the more minerals, the “harder” your water is).

Eventually, those minerals are going to crystalize in your plumbing system, causing a grey or white chalky-looking texture called limescale on surfaces where water touches.

That, of course, includes your water heater.

In a conventional storage water heater, minerals can accumulate at the bottom of your storage tank as sediment, which, if not flushed regularly, can reduce efficiency and even lead to premature equipment breakdown.

Since a tankless water heater doesn’t have a storage tank, that’s not an issue. However, the scale can still be a big problem on your tankless water heater’s heat exchanger (unless, of course, you install a water softening system).

Limescale On A Tankless Water Heater

When limescale builds up on the heat exchanger of a tankless water heater, your efficiency could drop by as much as 30 percent – essentially negating the efficiency benefits of using a tankless vs tank system.

The good news is it’s relatively easy to avoid a build-up of scale in your tankless water heater with a small investment of time and equipment.

How To Flush Your Tankless Water Heater

Please note: Before you try it yourself, always read the instructions the manufacturer gave you first! While the procedure detailed below is fairly standard, there might be slight but important variations based on your particular model. If you’re not comfortable tackling this procedure, don’t worry – we can take care of it for you. Just give us a call!

What you’ll need

• A tankless water heater flush pump
• Rubber or washing machine hoses to attach to the valves
• A water collecting bucket
• Vinegar or a tankless water heater descaling solution
• A channel lock wrench

Typical steps to descale a tankless water heater

1. Before you begin, set your temperature to 150°F and let hot water run through the heater for about a minute.
2. Shut off all the power to the water heater.
3. Close the incoming and outgoing water isolation valves. If your unit doesn’t have isolation valves, then you can buy some and install them yourself.
4. Have a bucket ready to collect water as it drains. There will be about a liter of water or so in the pipes of the tankless heater.
5. Drain the unit and connect hoses to the drain ports of the isolation valves “A” and “B”.
6. Dump this bucket or have another bucket ready to go with a solution to be pumped through the heater.
7. Fill an empty bucket with a mix descaling solution and water. About half a bucket of water will do the trick.
8. Open the isolation valves A and B.
9. Turn on the circulation pump. Let the solution circulate through the tankless water heater for at least 30 minutes, but an hour is better.
10. Drain the descaling solution from the heater and flush freshwater through the heater by closing valve “B”.
11. Open up valve “A” with a hose leading to an empty bucket.
12. Open up the inlet water valve to let freshwater flow through the unit and empty it into the empty bucket to get all of the solution out of the heat exchanger.

Descaling is not the only maintenance your water heater needs! Be sure to contact a water heater maintenance professional a minimum of once every two years for a conventional water heater, and once a year for a tankless water heater, to keep it running at its safest and best. Contact Ace-Robbins today to learn more about water heater maintenance in Wyoming County, PA!