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Old 05-23-2011, 07:17 PM   #1
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BackFlow Preventers and Pressure Reducers!


I am renovating a 1920 house! The house is a duplex and now being turned into a triplex. My next mission is the plumbing. I am using Pex. The main line will be 1" with 3/4" branches and 1/2" copper stub outs connected to compression fitting stop valves. My water pressure is around 100psi(city water). So I am going to have to install a Pressure Reducer Valve. I have been reading a lot online, and it says PRV's make it a closed system. Will I have to install expansion tanks on all 3 water heaters? Where do I install the PRV? Do I need a Back flow Preventer? If so, does that go before or after the PRV? I know I need a BFP on my sill cocks and if I am having irrigation. My city is based off the Uniform Plumbing Code. I have the IPC because the bookstore didn't have the UPC. I am just trying to make sure that I get everything lined up before I have to redo things. I have everything figured out except the dang PRV and BFP. I am sure the manufactuer has instructions or I can call the inspector but I would like to hear other opinions.

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Old 05-23-2011, 08:01 PM   #2
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BackFlow Preventers and Pressure Reducers!


Your PRV should be in the house, after the shut off valve. Preferably in a location always accessible for service. Set it for about 60#, no more then 80#
With a PRV, you will need expansion tanks. My UPC inspector says one for every heater. Not sure if I'm convinced though.
As far as backflow prevention goes, it will be up to your inspector. Usually not required here.

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Old 05-23-2011, 08:11 PM   #3
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BackFlow Preventers and Pressure Reducers!


Why do you need an expansion tank with a PRV?
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Old 05-23-2011, 08:25 PM   #4
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BackFlow Preventers and Pressure Reducers!


Quote:
Originally Posted by secutanudu View Post
Why do you need an expansion tank with a PRV?
Simply put- PRV's have spring loaded diaphragms that open and close as needed. If closed, excessive pressure caused by hot water expansion cannot be absorbed into the water main.
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Old 06-02-2011, 05:47 PM   #5
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BackFlow Preventers and Pressure Reducers!


I think some PRV valves allow backflow - at least I'm quite sure the one I bought and installed stated that it did. *shrug*.
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Old 06-03-2011, 08:23 AM   #6
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If PRV's were real backflow preventors, we wouldn't need backflow preventors. Heard this arguement a bjillion times.

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