On-Demand Hot Water Heater

Cleaning Scale

The industry standard is 45 mins at least once a year, but since yours is a bit behind schedule I'd do it for a while longer and might even replenish the vinegar halfway through. Dunno, never doned it, but you should be able to tell if debris is still coming out.

http://homeguides.sfgate.com/flush-out-tankless-hot-water-heater-53060.html

https://www.wikihow.com/Maintain-a-Tankless-Water-Heater

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