How often should you descale your tankless water heater?

Skipping it eventually leads to water damage or an expensive repair.

Staying on schedule matters beyond the repair bill: a consistent maintenance record is one of the factors in a home's Roots Home Health Score, and well-kept homes typically sell faster and closer to asking price.

How to do it

A tankless heater flashes water hot across a heat exchanger, and hard-water minerals scale up on that exchanger fast. Descaling with a pump and vinegar or descaler restores flow and efficiency.

1. Shut off the gas or power and close the hot and cold isolation valves.
2. Connect a small pump and hoses to the service ports and circulate vinegar or descaling solution for about 45 minutes.
3. Flush with clean water, reopen the valves, and restore power.
4. Clean the inlet screen while you're at it (its own task).

Alternatives & optional extras

• Homes with a water softener scale up far slower and can stretch to every 18–24 months.
• Install isolation valves with service ports if yours lacks them; it makes every future descale a 10-minute hookup.

Time: ~1 hour · Typical cost: $20–$40 for a descale kit; $150–$250 for a pro service

What you'll need

• Tankless descaling kit (pump + solution)

If you skip it

Scale buildup chokes flow and efficiency and, left long enough, overheats and damages the heat exchanger, the costliest part.

Other tankless water heater maintenance

• Clean tankless inlet water filter — once a year

Related systems to keep on schedule

• Boiler / radiators — start with: schedule boiler service, once a year, ideally in September
• Furnace / heating system — start with: replace hvac air filter, every 3 months
• Mini-split / ductless AC — start with: clean mini-split filters, once a month
• Air conditioner — start with: schedule ac tune-up, once a year, ideally in April