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Thread: Optimal PSI for house water

  1. #1
    DIY Member shluffer's Avatar
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    Default Optimal PSI for house water

    I noticed that my water supply from the street has a peasure reducing fitting on it. The preasure is currently set to 25 PSI and it has a range from 25-75 PSI. I am looking to install an RODI system, which requires water preasure of at least 50 PSI.

    I have a couple of questions about this:
    1) i have an old house with old plumbing. How much of a risk is it to increase the PSI to 50 or 60?
    2) Is there an optimal PSI to set it to? Is it better off at this lower number (and I'll need a pump ofr the RODI) or is a higher preasure better?
    3) The preasure gage has been on the pipe for years. Do they go bad? Should i replace the gage before increasing the preasure to make sure its reading correctly?

    I'm thinking that this is also the reason that we don't allways get great water preasure in the shower upstairs, and that it takes forever for our washing machine and dishwasher to fill.

    Thanks in advance for the help.
    Last edited by shluffer; 03-08-2010 at 07:17 PM.

  2. #2
    Moderator & Master Plumber hj's Avatar
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    My customers would NEVER be satisfied with anything less than 60 to 75 psi at the house. How long does it take you to fill a glass of water at that abysmal pressure? If the plumbing cannot handle at least 60 psi, then it will not be long before you have problems at 25 psi.

  3. #3
    DIY Member shluffer's Avatar
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    I would agree with your customers. The preasure is ridiculous.

    Filling a glass of water takes way to long. I fill 5 gallon buckets for my fish tank. it takes forever.

    Do I replace the preasure gage to conferm that its correct, or should I just start increasing the preasure?

    When I increase the preasure, do I do it all at once, or should I do it slowly over a couple of days?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Buy yourself a new gauge to check the one installed. You shouldn't need to ramp the pressure, you should be able to just go there. Keep in mind that if you have a weak valve or seal, it may start to leak, but that should be obvious and it should just go down the drain while you look around. IF something let go, you'd hear the flow while you were adjusting things. With the PRV, you should have an expansion tank. This (depending on the type) will often have a bladder. That bladder needs to have its air charge increased to the same value as the pressure you are making the water. You can only adjust that pressure when the water pressure is off (i.e., the supply closed and a valve open to relieve any pressure in the line).

    The increased flow might dislodge any accumulated crud in the lines, and you may need to clean showerheads, faucet aerators, etc. out from the crud.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    DIY Member shluffer's Avatar
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    I don't have an expansion tank. My valve looks like the Watts Water Pressure Reducing Valve Series 25AUB-Z3 3/4" (0069717). I tried to include a link but it gets ****** out.

    The adjustment is just a screw that you srew in to increase the preasure. I have a similar (smaller) device on my boiler which works the same way.

    I was under the impression that expansion tanks are used when there is hot water is involved to prevent the preasure from increasing as the water heats. That would not be the case here.

    Is there a bladded that may be hidden somewhere, or am I still at just increasing the preasure?
    Last edited by shluffer; 03-09-2010 at 10:14 AM.

  6. #6
    Master Plumber-Gas Fitter shacko's Avatar
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    "I was under the impression that expansion tanks are used when there is hot water is involved to prevent the preasure from increasing as the water heats. That would not be the case here."

    You have a water heater don't you? expansion tanks will keep your T+P valve from leaking when the heater is on; you always need them when you have a PRV in your system and when the municipal system has a check valve in it.

  7. #7
    DIY Member shluffer's Avatar
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    This explains alot. I do not currently have a expansion tank on my system, but the preasure release valve on my water tank does leak from time to time.

    I'm not sure if there is a check valve between me and the city. I will have to check.

    Do I need to add an expansion tank to the system prior to increasing the PSI?

    This project seems like its growing.

  8. #8
    DIY Member shluffer's Avatar
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    How long do these valves last? I turned the adjustment screw in and the preasure did not increase.

    The valve looks like it has been thre for a while. Is there a way to test it?

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    The PRV IS a check valve in itself, so yes, when you have one, you need an expansion tank. A PRV can last anywhere from days to many years. How old is yours?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #10
    DIY Member shluffer's Avatar
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    nfortunatly, I have no way of knowing. We have been in the house for 6 years and it predates us. The gentelman living here prior to us was here for for 60 years. If I had to guess, I would say at least 10 possibly longer. Its a watts u5b if you happen to know when they stopped making it. they now are making the u5bz3.

    Regardless, it does not seem to work. When I titen the adjustment, the preasure does not increase.

    I picked up a new preasure gage and will try it out.

    Where do I put the expansion tank? can it go anywhere on the system?

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    the expansion tank should go anywhere on the COLD side of your water system and ideally after the shutoff to the WH so if that ran, the expansion tank would still be able to absorb the expanding water caused by the heating. There are diagrams and siziing calculators on the www.watts.com site. You don't want it on the hot side, because it jsut won't last that long. The PRV essentially blocks flow back towards the supply (some have a high-pressure bypass), so after refilling the WH with cold water, once it gets heated and expands, the pressure rises and it has to go somewhere. This could be through a weak valve, or if they all can handle it, out the PRV safety device on the WH. Another common failure point is the supply hoses to things like the Washing machine, faucets, toilets, and icemakers. The PRV trips at 150#, and since water doesn't compress, it doesn't take much expansion to reach that point. Your copper water lines don't stretch much...the water will win. Thus, the expansion tank was invented to solve the problem. Keeping the water pressure within normal limits lengthens the life of all of your plumbing stuff.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    Moderator & Master Plumber hj's Avatar
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    You could have low pressure because your PRV has gone bad, in which case it may not adjust, or be erratic when you do adjust it. IF there is a hose faucet by the PRV, which is often the case, then get a pressure gauge which screws onto it, and then adjust the PRV while watching the gauge.

  13. #13
    DIY Member shluffer's Avatar
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    I am now the proud new owner of a new valve.

    I have a tee just past the valve that I will be connecting a new preasure gage to.

    It looks like it shoul be an easy job, but nothing is ever as easy as it should be.

  14. #14
    In the Trades Gary Swart's Avatar
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    That was a good idea to put the gauge in the tee. When you get an expansion tank, the tank is air charged with a bicycle air pump. I has a Schrader valve just like a tire. The pressure in the tank should match the PRV setting. Be careful when charging the tank, it doesn't take much air volume, and if you are not checking the pressure frequently, you can rupture the bladder in the tank.

  15. #15
    DIY Member shluffer's Avatar
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    I installed the new valve. Took less time than I figured, and only ran into one poblem. Not bad.

    The valve seems to be factory preset at 40PSI rather than the 50PSI they claimed. Should this concern me? I'm thinking that as long as the preasure increases when I tighten the screw, i shouldn't worry about it.

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