# open or closed system



## C.C.R. (May 19, 2006)

How do you tell the differance between open and closed system? The plumber I use on my jobs was talking about this.


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## mdshunk (Mar 13, 2005)

PRV and check at entrance... closed. Everything else, nope.


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## JamesNLA (Jun 2, 2006)

If you have a closed system you might want to learn about an expansion tank. In a closed system there is no compression of water (or very little) When water heats up it expands a little bit. So if the piping the water is contained in is sealed and you heat some of that water, where does the expanding water go? One place is through the seems of your tanked water heater, or maybe a joint that wasn't that good to begin with. With the Xpantion tank this will take care of that problem. You need to find out what kind of pressure regulator valve you have at the house entrance. If there is a check valve inside there you are on a closed system. Poor mans way to test it is get a pressure valve to hosebib ($10 at any supply store) attach valve to hose bib and turn bib on, you then have your house pressure, make a note of that.

Now, go turn on some hot water fixture for a few minutes. Shut it off and go watch the pressure valve. Your looking for a slight increase in pressure. If you get a steedy read, you are on a closed system, if you have a swinging gauge that is the measurment of water comming in and out of the house from your city supply.


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## TurdMaster (Mar 16, 2007)

C.C.R. said:


> How do you tell the differance between open and closed system? The plumber I use on my jobs was talking about this.


A closed system has a dual check backflow preventer on the water service. There are certain provisions you have to take into account when you have this type of system, such as expansion tanks and PRV's.


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