Common tankless water heater problems in Utah homes — and which ones a flush fixes

Tankless units are reliable, but they're sensitive to water quality, and Utah water is hard. Below are the symptoms we hear most, what usually causes them, and whether a flush is the fix.

Hot water takes forever, or comes and goes

Usually: scale on the heat exchanger, or a scaled flow sensor. The unit is struggling to read flow and modulate the burner. Fix: a flush, most of the time. If it persists after a flush, the flow sensor or a mixing valve is the next suspect.

Low flow at the taps, especially hot

Usually: the inlet filter screen is packed with sediment, or the exchanger passages have narrowed. Fix: clean the screen (we do this on every visit) and flush.

Rumbling, popping, or kettling noise

Usually: water flashing to steam against scale deposits. This is the unit telling you it's overdue. Fix: flush. Don't wait — this is how heat exchangers crack.

Error codes

Every brand has a scale or maintenance code (Rinnai's "LC" codes are the best-known example; your manual has the list). Those clear after a descale. Ignition and venting codes are a different category: call us or a plumber before resetting repeatedly.

No hot water at all

Check the obvious first: is the gas on, is the unit powered, is the display showing anything? A tripped GFCI or a closed gas valve after other work in the house is common. If it's an error code, see above. If the unit is dead, that's a service call, not a flush.

Water at the base of the unit

Condensing units produce condensate by design — but it should go down a drain, not on the floor. Otherwise a drip is a fitting, a relief valve, or (worst case) the heat exchanger. Shut the water to the unit and call. Leaks don't fix themselves.

Five things you can do between visits

1. Keep the area around the unit clear so it can breathe and so we can get to it.
2. Check the inlet filter screen twice a year if you're on a well or have sediment.
3. Set the temperature at 120°F. Higher runs the burner harder and scales faster.
4. If you have a softener, keep it salted — it's protecting the heater more than anything else.
5. Book the flush once a year. It's the one item that keeps the warranty valid.