Service
Tankless Water Heater Repair
Diagnosis and repair of on-demand water heaters, including error codes, scaled heat exchangers, ignition faults and inadequate flow.
- Licensed and insured
- Price agreed before work
- A plumber who works your area
The display is telling you something
Unlike a tank, a tankless unit reports its own faults, and that is a diagnostic worth using.
Error codes map to specific causes: ignition failure, flame loss, overheating, insufficient flow, venting problems. Reading the code and checking it against the manufacturer’s list narrows the cause in minutes.
Note it down before switching the unit off, because power cycling often clears the display and takes the information with it.
Not the unit, the supply
A large share of tankless faults are not faults in the heater at all.
Flow. These units need a minimum flow rate to fire. A partly closed valve, a blocked inlet filter or a heavily scaled fixture can drop the rate below the threshold, and the heater simply does not start.
Gas. Tankless units draw a lot of gas at full demand, far more than the tank they replaced. If the line was never upsized at installation, the unit underperforms or faults when other appliances are running, and no amount of work on the heater will fix it.
Scale. In hard water, deposits on the heat exchanger insulate it and output falls off gradually. That is maintenance rather than repair, and it is the single most common reason a tankless unit disappoints its owner.
Does this sound familiar?
Problems this service solves
- An error code on the display and no hot water
- Water that runs hot then cold during a shower
- A unit that will not fire at low flow
- Declining output in a hard-water area
- Ignition failures on a gas unit
Signs you need tankless water heater repair
If more than one of these is true, the problem is usually past the point a plunger or a store-bought cleaner will fix.
- The unit is displaying a fault code
- Hot water arrives, disappears and returns
- The heater will not start unless the tap is fully open
- Output has fallen off gradually over a year or two
What to expect
How the visit works
Read the code properly
Tankless units report specific faults. The code narrows the cause immediately, and ignoring it in favour of guesswork wastes the diagnostic the manufacturer built in.
Check flow and gas
Many tankless faults are supply problems rather than unit problems: insufficient flow to trigger firing, or a gas line that cannot deliver enough at full demand.
Descale the exchanger
In hard water the heat exchanger scales up, which shows as declining output and eventually as faults. Flushing with a descaling solution restores it.
Repair or advise
Igniters, flame sensors, flow sensors and valves are replaceable. Where the exchanger itself has failed, you get told what that means economically.
What's included
What you get on every job, whoever we send.
- Fault codes used as the diagnostic they are
- Supply problems distinguished from unit failures
- Descaling as a real repair, not an upsell
- Honest economics when a major component has failed
Questions
Tankless Water Heater Repair questions
My tankless heater goes hot then cold. What is that?
Usually the cold water sandwich, and it is characteristic of on-demand heating rather than a fault. When hot water is drawn intermittently, the slug of water sitting in the pipe from the last draw arrives first, followed by cold water that the unit has not heated yet, followed by properly heated water. Some units and recirculation setups manage it better than others. If it is severe or new, it is worth checking flow sensors and the minimum activation rate.
Why has my tankless heater got weaker over time?
Scale on the heat exchanger, almost certainly, if you are in a hard-water area. Minerals deposit on the exchanger surfaces and insulate them, so less heat transfers to the water and output falls. It is gradual, which is why it is often mistaken for the unit ageing. Flushing with a descaling solution restores performance, and doing it on a schedule prevents the decline rather than reversing it.
Does a tankless unit need servicing?
Yes, more than people expect when they buy one. Descaling on a schedule is the main item, and the interval depends on your water hardness rather than on a generic recommendation. The inlet filter needs cleaning, and gas units need their combustion and venting checked. A tankless heater that is never serviced in hard water will underperform within a few years and can fail early.
Related services
Tankless Water Heater Installation
Installing on-demand water heaters, including the gas line sizing, venting and condensate handling that the unit itself does not come with.
See what this coversWater Heater Repair
Diagnosis and repair of gas, electric and tankless water heaters, including no-hot-water calls, leaks, pilot problems and sediment flushing.
See what this coversWater Heater Maintenance
Annual servicing that extends water heater life: flushing sediment, checking the anode rod, testing the relief valve and verifying the venting.
See what this coversLeak Detection
Locating hidden water leaks under slabs, inside walls, in yards and at the meter using acoustic, thermal and pressure-testing equipment, then repairing them.
See what this covers
Get it fixed
Tankless Water Heater Repair, handled locally
Call with your ZIP code and what you are seeing. We route you to a licensed plumber in your area who does tankless water heater repair every week.
- Licensed and insured
- Answered 24/7
- Price before work