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Old 03-05-2012, 19:31   #1
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water heater check valve

I have a question about water heater installation. Is it required to install a check valve in the inlet line to the water heater ? I would guess that it would stop pressure from the heated water to back up to the pump. Is this really needed or is it like the now obsolete accumulator tank due to the newer pump designs ? I have just installed one of the new vari-speed pumps and at the cost of that pump really wouldn't want it damaged from pressure from the water heater.
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Old 03-05-2012, 19:39   #2
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Re: water heater check valve

At least on my boat with a pretty std 12-gal Raritan wtr htr, the check valve is to stop the flow of hot water back into the cold circuit so you don't initially get hot when you want cold.
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Old 03-05-2012, 20:06   #3
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Re: water heater check valve

So maybe it is a check for water flow instead of excessive pressure at the pump head ?
Just don't want to damage the new pump or void the warranty.
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Old 03-05-2012, 20:50   #4
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Re: water heater check valve

Could be, but I'd be sure to check the manual for the pump.
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Old 03-05-2012, 21:16   #5
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Re: water heater check valve

one issue with check valves at water heaters is thermal expansion, when the water is heated in the tank. Options are:

1. Just let the relief valve pop, though sometimes the relief will not pop (so messy when that happens) and sometimes it will not reset, dripping water into the bilge and draining your water tank. Also does not meet current plumbing codes (in the USA anyway) btw.

2. Drill a small 1/8" hole in the check valve clapper. This was the old school way of relieving pressure back to the cold water side, while keeping the hot water in the tank. Before Oh 1998 ish this was standard practice in engineered plumbing design.

3. Install a thermal expansion tank between the check valve and the water heater. This is the current "code" method for dealing with thermal expansion at water heaters. I recommend the small ones at the big box store over the more expensive marine "accumulator" version.
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