Standby DHW Tank Question

Cyclist77

SInce installing our indirect dhw tank with the new boiler I have a question. We kept the electric dhw tank and isolated it to be used as a backup. Last night I started wondering about the water in the tank. Should it be drained and refilled every so often?

Thanks!

Jamie Hall

Funny how things show up in the middle of the night…

The answer to your question is n— yes it should. While stagnant water is usually OK, it can decide to grow nasties…

How often? Well… At the very least weekly, I'd say. And if it's that rarely, I'd run it right up to 140 F and hold it there for an hour every time it is refilled, then turn it off. But I'm sort of conc=servative.

An alternative would be to pipe it so that the feed to the regular domestic hot water went through it first, but without heating it. That will keep the water in it fresh at all times, and is probably what I would arrange.

hot_rod

You could valve and series the tanks, so fresh water always flows through the electric tank first. If the indirect is down you could valve it off, flick on the electric tank breaker.

This also give you a small amount of pre-heat the first tank being at ambient room temperature.