Tankless water heater faults, codes and repair
Quick answer
Record the model, fuel type and error code before resetting a tankless heater. Ignition, flow, scale, venting and control faults need different checks. Use the manufacturer's manual for the exact model; a code alone is not a parts diagnosis.
Cold water, shutdowns and leaks
A heater that never starts, starts then stops, or alternates hot and cold may have different causes. Note whether every fixture is affected and whether the fault happens only with several taps running. Demand above the heater's capacity can also lower delivered temperature.
For an active leak, shut down heat or power if it is safe and contact a qualified technician. If you smell gas or a carbon monoxide alarm sounds, leave and call for emergency help from outside.
Brands, manuals and training
QWH repairs major gas tankless brands including Navien, Noritz, Rinnai, Takagi and Rheem. Confirm the exact model before booking. A Bosch or other older unit may need a manufacturer specialist or parts availability check.
A service manual is written for trained technicians and does not make live gas or electrical testing safe for an untrained homeowner. Manufacturer training and the correct diagnostic equipment matter. Do not bypass flow sensors or combustion safeguards.
Maintenance and heat exchanger faults
Plan for annual maintenance following the manufacturer's manual. A water softener or scale prevention system can reduce mineral buildup and the need for descaling, but it does not replace checks of the venting, air filter, condensate system and safety controls. Descaling frequency depends on water quality, usage and the model.
A leaking heat exchanger needs assessment for replacement and possible manufacturer coverage. Cleaning does not repair a cracked exchanger. A quote should identify the failed part, parts availability and any venting or water quality correction needed.
Electric and propane models
QWH does not install or service electric tankless heaters, including electric instant models. Contact the manufacturer or a qualified electric tankless specialist. Propane gas units also need confirmation of fuel specific parts and service coverage before booking.
Rather we did it?
Current repair prices and booking