Tankless water heater clogged

[Frank Pratt]

I like Kev's idea. Lots of farting around, but if it save the price of a new heater, might be worth it.

[Mike Henderson]

Those tankless heaters have many small tubes that the water goes through. It's the only way the water can be heated that quickly as it passes through the heater.

If your problem is that the tubes are clogged, some of those tubes may stay clogged even after you get flow through the heater.

But having EVERY tube clogged such that nothing goes through the heater seems very unusual. If the tubes were clogging up, I would expect the flow to have decreased over time. Maybe there some single point of clog that you're dealing with.

Mike

[Bruce King]

Probably these corroded.

[Thomas McCurnin]

They actually make a designated product for the annual flushing of tankless heaters, not vinegar, and a couple of years ago introduced tankless water filters which prefilter the water with replaceable paper filters and a pressure gauge showing when the filter should be replaced. Noritz says it reduces the flushing frequency. I own a Noritz, flush every year using the Noritz recommended product, and installed the filter.