Tankless Water Heater Repair
Quick answer
Most tankless problems are scale on the heat exchanger, a clogged inlet filter, a failed flow sensor or igniter, or venting and gas supply faults, and the unit's error code usually points to which. HomeAdvisor puts tankless repair at $75–$1,300, about $600 on average. Call (888) 217-6781 for a plumber who services tankless units in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Signs you need a plumber
- An error code on the display
- Hot water that turns cold mid-shower
- No hot water at low flow
- The unit will not fire or shuts off
- Hot water that takes longer to arrive than it used to
If you smell gas near a gas tankless heater, leave the house and call the gas utility from outside before calling a plumber.
What to check before you call
- Write down the error code and the model number
- Clean the cold-water inlet filter screen
- Check that the gas valve is open and other gas appliances work
- Ask when it was last descaled (flushed)
What the plumber does
- 1
Reads the code
Uses the error code and the unit's diagnostics to narrow it to a part or a supply problem.
- 2
Descales and cleans
Flushes the heat exchanger with descaler through the service valves and cleans the filters.
- 3
Replaces the part
Flow sensor, igniter, flame rod, fan or board, then test-fires the unit.
Tankless water heater repair cost
| Job | Typical range | Source |
|---|---|---|
| Tankless repair | $75–$1,300 (average about $600) | HomeAdvisor |
| Tankless repair, national | $100–$650 | Fixr |
Hard water areas need descaling about once a year; skipping it is a common cause of tankless failures. Sources: HomeAdvisor cost guides (2025), Fixr cost guides (2025).
Ready to book a plumber?
One call reaches a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Tankless water heater repair: common questions
Why does my tankless water heater go cold mid-shower?
Often the flow drops below the unit's minimum to stay lit, or scale is choking the heat exchanger. A clogged inlet filter or a failing flow sensor does the same.
How often should a tankless water heater be flushed?
About once a year in most homes, more often with hard water. Check the manufacturer's manual for your model.
Is a tankless water heater worth repairing?
Usually, since tankless units last around 15–20 years. Sensors, igniters and descaling are routine; a cracked heat exchanger on an older unit may not be worth it.
Other plumbing services
(888) 217-6781 is the plumbing line. HearthDry is a referral service; the company you reach is independent.