Best location for Thermal Expansion Tank and Pressure Reducing valve?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by bobwood, Mar 10, 2008.

  1. bobwood

    bobwood New Member

    Mar 2, 2008
    I measured my water pressure this weekend and am at 80psi plus. I would like some advice on the best location (and brand) for both the Pressure Regulating Valve and Thermal Expansion Tank. I was planning to put the valve just past the ball valve shutoff for the house. Can I locate the Expansion Tank nearby or does it have to be closer to the hot water heater? This location would be about 20' away from the hot water heater.

    From reading the posts looks like Sharkbites would not be the best choice, I'm assuming the same opinion holds for compression fittings?

    The nice thing is I have space in this area to work and to put the tank out of sight. Given my concrete walls do you hang the tank (in case it fails and gets water logged) or put it on the floor? I've visited the Watts site to determine the size tank I'll need.

    Thanks in advance for the help.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    The tank can be anywhere after the PRV on the cold side. For replacement, it is a little neater to hang it and use a valve on the T so you don't need to shut the whole house off. You need to support the pipe either side of the T or use straps on the tank. You want access to the air valve. If you don't have a water pressure gauge, once the system is up, you can use that to check the system water pressure using a tire pressure gauge. Precharge the air tank before installation to the working pressure (they usually come with about 40#). Because it isn't a very big tank, be careful when pumping it up to avoid overcharging it.

    Last edited by a moderator: Jun 12, 2008
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  4. Redwood

    Redwood Master Plumber

    Dec 15, 2007
    Service Plumber
    The best location for the PRV is shortly after the meter wherever convenient Before anything splits off the line so that all fixtures are protected.

    The Thermal expansion tank should go between the water heater shut off valve on the cold side and the water heater itself. The physical location of the tank does not have to be there but the tee it connects to should be. A valve is not a bad idea on the expansion tank line. It will aid in replacing the tank as will having the threaded connection on the tank facing up.

    BTW did you use a lazy hand gauge to record the pressure over a 24 hour period? Quite often pressures are boosted over night as the water company tops off their storage tanks.
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