Tankless Water Heater Descaling & Maintenance
Hard water builds scale inside tankless water heaters. A yearly descaling and checkup keeps yours running and lasting longer.
Updated October 2026 · By the Hot Water Heater Factory team
Why do tankless water heaters need descaling?
Hard water leaves calcium and other minerals behind when it’s heated. In a tankless water heater, that scale coats the inside of the heat exchanger, where the water passes through narrow passages. Scale makes the unit work harder, can make it overheat, and is one of the most common reasons a tankless water heater shows an error code or fails early.
How often should a tankless water heater be descaled?
| Your situation | Typical schedule |
|---|---|
| Hard water, no softener (most Inland Empire homes) | About once a year |
| Water softener or scale filter | Less often; we check and tell you |
| Heavy use, large family or business | More often, sometimes twice a year |
Follow your manufacturer’s schedule too. Some units warn you: Rinnai tankless water heaters show code LC when scale is building up in the heat exchanger.
What are the signs a tankless water heater needs descaling?
- Water temperature goes up and down
- Less hot water flow than before
- A scale or overheating code, such as Rinnai LC or Noritz 16
- Banging or rumbling noises
- It’s been more than a year since the last service
What’s included in a tankless maintenance visit?
- Descale the heat exchanger by circulating a descaling solution through it
- Clean the cold-water inlet filter
- Clean the air intake filter, on models that have one
- Check the venting and the condensate drain
- Check gas pressure and burner operation
- Check the error code history and the relief valve
If your tankless doesn’t have service valves for flushing, we can install them so future maintenance is quick.
Can I descale a tankless water heater myself?
Some homeowners do, if service valves are installed. A full visit also catches the problems a flush doesn’t, like a weak gas supply, a blocked vent or a failing part, before they leave you without hot water.
Seeing a code? See tankless error codes. More on tankless installation and repair.
Related
Tankless maintenance near you:
Questions we hear a lot
How long does tankless descaling take?
The descaling itself usually takes about an hour. A full maintenance visit with filter cleaning and safety checks takes a little longer.
What happens if I never descale my tankless water heater?
Scale keeps building up. The unit loses efficiency, may overheat and shut down with error codes, and the heat exchanger can fail early, which is often the most expensive part to replace.
Does a water softener mean I never need to descale?
It means you need to descale much less often. Softened water leaves far less scale, but the unit still benefits from a periodic checkup.
Do you maintain all brands of tankless water heaters?
Yes, including Rinnai, Navien, Noritz, Takagi, Bosch and A.O. Smith.
Time for a descaling? Text us now.
Send a photo of your water heater’s label and tell us what’s happening. A real person texts you back.