Water – When do tankless water heaters need to be descaled

maintenancetanklesswaterwater-heaterwater-softener

I had a Bosch tankless natural gas water heater that stopped working with C7 and EA error codes and the plumber indicated that the unit had failed due to water getting into the internals like the fan an circuit board. The plumber said this was due to the tankless never having been descaled and that the unit should be descaled annually.

Under what situations should a tankless water heater be descaled? Does it depend upon how hard your water is? Can you add some kind of filter before the intake to reduce the need for descaling? If descaling should be done periodically, how can I determine the right frequency for my situation?

Best Answer

The manual will say something like

Flushing the heat exchanger with a descaling solution if mineral build up is evident. Scale build up will shorten the life of the water heater, descale heat exchanger thoroughly and repeat annually depending on mineral content of ground water.

(From Bosch 2400E NG user manual)

or maybe something like

Periodic descaling may be necessary in areas with high mineral content in the water. Scale buildup in the heat exchanger may result in lower flow rates, error codes of A7 and E9 and boiling sounds (knocking and banging) in the heat exchanger.

(From Bosch GWH 2400 ES NG User Manual)

so

Under what situations should a tankless hot water heater be descaled?

When mineral build up is evident on annual inspection.

Does it depend upon how hard your water is?

Yes

If descaling should be done periodically, how can I determine the right frequency for my situation?

By inspection.

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