# Thermal Expansion



## robthaplumber (Jan 27, 2010)

A thermal expansion tank is required by code only on a closed system. This means a check valve, pump sys. w/solonoid, and prv without integral bypass has been installed. Do the integral bypass prv's really work? I've had to install expansion tanks even with an integral bypass prv to prevent T&P discharging.


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## SlickRick (Sep 3, 2009)

Rob, I didn't mean a discussion with yourself. Find a current topic your interested in. It's going to be alright.


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## Protech (Sep 22, 2008)

Those integral bypasses won't work if the high pressure side of the PRV is over 80PSI. It will only dump the pressure back into the municipal system at the pressure the municipal system is at. I really don't see the point of those integral bypasses other than a last layer of defense.


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## Miguel (Aug 10, 2009)

If the expansion tank alone isn't doing the job then it's either undersized or something else is screwy.

_This reminds me of something . . .:001_unsure: Crap! WHat was it?_

Btw, Hi robthaplumber. Welcome to the Zone.


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## Bill (Jun 17, 2008)

Miguel said:


> This reminds me of something . . .:001_unsure: Crap! WHat was it?


What? Are you getting old? They say the first thing to go when you get old is, uhh, I ummm, let me see, no thats not it, umm, maybe.......Oh heck, someone give me a clue:laughing:


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## Plumber Jim (Jun 19, 2008)

The bypass works upto the outside city pressure. so if you had a city pressure of 100 psi then the pressure wouldn't go over 100 psi. So you always need to know the pressure on the city side of the prv if you are depending on that bypass to work. I just installed an expansion tank the other day because the guy had some company replace his main and they put in a prv and it didn't have a bypass but they didn't bother to tell him that it would make his T&P pop. Oh, and this was an inspected job too. lol


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