How to hydrostatic test Pex install?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Treygrey, Apr 14, 2013.

  1. Treygrey

    Treygrey New Member

    Messages:
    3
    Location:
    British Columbia
    Could someone advise on how I should test my pex water supply for a bathroom remodel? The city inspector says 200lbs of water using a hydrostatic pump. I think a local rental place has a pump I can rent, something like this?

    6381.jpg

    But how to do the test? I have a home run layout running from two four-way copper manifold for hot and cold, with shut off valves separating the manifolds from the existing plumbing. I use three of the manifold connections for the cold supply (shower, wc, lav) and two for the hot (lav, shower) so I have connections available for the test, if necessary.

    I'm thinking that the correct way to test would be to
    1) cap off the ends of the lines
    2) Attach pump to spare connection on cold manifold
    3) Open valve to fill system
    4) Close valve
    5) Pump to 200lbs


    Repeat 2 - 5 for hot manifold

    Thank you for your help.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    Essentially correct, but depending on how long the test has to be in place, any air in the system could be absorbed into the water dropping the pressure, AND the tubing could, and probably will, expand, also dropping the pressure so you may have to "top off" the pressure a few times.
  3. Treygrey

    Treygrey New Member

    Messages:
    3
    Location:
    British Columbia
    Thanks for the confirmation hj. Fingers crossed, hopefully it will be OK. All this seems to be overkill for pex (wouldn't just filling the system be sufficient?) but what the inspector says goes.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    FWIW, I looked at the spec sheet on Wirsbo's pex, and depending on temperature, the highest pressure it is spec'ed for is 160psi at 73.4 degrees F http://www.uponor-usa.com/~/media/Files/Technical%20Documents/Commercial%20Related%20Docs/AQUAPEXTubing_TB_9_06.aspx?sc_lang=en. I would be very nervous about pumping it up to 200psi. Since no residential water supply system is supposed to experience any more than 80psi without a pressure reduction valve...double that seems like more than enough. Is that 200psi figure written down, our just his WAG at what's right? Just seems wrong to me. Check the spec sheet of the pex you're using, and see if he'll agree to a more reasonable pressure based on that. Now, most copper installations should take that without issues, but valves may not like it (might blow out an o-ring or other seal).
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    All plumbing is designed to work up to 150 psi working pressure, which is the setting of the water heater's relief valve, so the system should never exceed that pressure. Maybe the inspector is like a lot of us and doesn't like PEX, so he hopes it will "blow out" at that pressure.
  6. Treygrey

    Treygrey New Member

    Messages:
    3
    Location:
    British Columbia
    Hmmm looks like the Pex I got from Home Depot here in Canada is rated at 100PSI @ 180F so 200 psi is double its rating. And his reason for doing a hydrostatic test instead of an air test was that is was safer. Oh well, I'll hook everything up and when he comes round I can question him about the correct pressure based on the rating of the pipe. Thanks for all your input.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    All pex has changes in max pressure with temperature changes...lower the temperature, and it can handle more pressure. You would not be using 180-degree water to do a test and as potable water, would probably never see that temp, either since the WH would unlikely ever get that hot.
  8. nukeman

    nukeman Nuclear Engineer

    Messages:
    711
    Location:
    VA
    Around here, you only need to hydrostatically test to the working pressure of the system (usually turn the water on and pressurize to supply pressure). For non-plastic pipe, you can also air test to a minimum of 50 psi for 15 minutes.

    The 200 psi value seems excessive. The T&P valve on the water heater will open at 150 psi, so the system pressure should never exceed that value. To get to 200 psi on a real system, the T&P would have to fail, you would need to be on a closed system (PRV or check valve at meter), and there would have to be no expansion tank (or expansion tank failure). In this case, having a leaking supply is the least of your worries (it leaking would actually help you). Being in this situation would mean that your WH could become a rocket at any moment. :) The other way to get to 200 psi, would be the WH in the attic (or upper floor) of a building that was over 100' high could have piping at 200 psi (ground floor) when the T&P at the WH was at 150 psi. Again, you would need a closed system, etc. to get to this point.

    I would dig up the BC plumbing code and see what it says. There could be code changes at your local level too. The inspector will have the final call as to what he wants to see, but if the code book says 100 psi and he says 200 psi, you could ask him for a code reference for the 200 psi.
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