Hot Water Recirc Air Release

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Kekeken

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I am doing an upstairs bathroom remodel that presents an opportunity to install a hot water recirc line. The bathroom is the farthest point in the house from the hot water heater and is currently the high point in the water system. Since I have a slab foundation the only return route is through the attic. I am able to access both ends to run the pipe but this route will move the high point to the attic. Does a 1/2" copper recirc line need an air release valve at the new high point or will the velocity of the water in a 1/2" pipe flush out what little air might accumulate?
 

jadnashua

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There's plenty of water pressure in the potable supply to push water through that line once the valve is open. Might burp and sputter the first time it's used, but should be fine afterwards as long as the check valve operates. It might be a problem if it was a hydronic heating system, as they run at something like 12psi, versus at least 30, and probably lots more in the potable system...that's enough to push it up and any air out of the system.
 

John Gayewski

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You just need a way to isolate the recirc line from the water heater so you can purge at the water heater. Basically a way to valve it off so it runs in order. Water heater fills, supply piping fills, recirc line fills all of the air should purge back at the water heater recirc, then open the valve and it's ready to circulate.
 

Kekeken

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jadnashau - thanks for the response. Our water service is well above 45-psi so I would think it would be self-purging.
Gayeweski - I am a little unclear on what you are describing. By "isolating the recirc line from the water heater so you can purge AT the water heater" do you mean having a dump valve near the recirc pump at the water heater to flush the line after installation?
 

John Gayewski

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Yes. Water heater, piping, pump, check valve, isolation valve, water heater/drain. The isolation valve will only be operated to fill the recirc line after the air is let out at all of the fixtures and at the drain, after that you can just take the handle off so no one shuts it while the pump is running. But you should really just use the water heaters drain as a "dump valve" as your calling it.
 
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