Pressure-balancing valve = cold water on the hot water circuit?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jeffeverde, Sep 13, 2010.

  1. jeffeverde

    jeffeverde Member

    Messages:
    80
    Location:
    L.A.
    Will a pressure-balancing valve feed cold water to the hot water side when the hot water side is open? I had my water heater disconnected this weekend, with water off at the main supply. When I reconnected the water heater, I had the cold supply valve closed when I opened the main supply valve. Went to the water heater to open it's supply valve, and could hear water rushing in, with the valve closed??? Went inside to check a faucet and sure enough, I had cold water at full pressure on both the hot and cold side -- while the supply valve was still closed at the water heater.

    I was told this was because of a pressure-balancing valve. Is this normal function for a pressure-balancing valve, or is there something else going on? I've only got one mixer valve (tub/shower) in the house - everything else is two-handled faucets.
  2. Jerome2877

    Jerome2877 In the Trades

    Messages:
    397
    Location:
    BC
    So the valve for the shower/tub was open for hot and cold? Then yes this would feed the water into the hot side and back the the WH. If it wasn't open then no this shouldn't happen.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    It isn't the pressure balancing feature that does that . EVERY faucet...sink, tub, or shower performs the function of mixing hot and cold water. If you have any faucet set to a "warm" setting, or in the case of a two handle faucet, if you have both open, then water will cross over inside the faucet. In your case, cold water crossed over and back-fed the hot piping.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,303
    Location:
    Cave Creek, Arizona
    A pressure balancing unit does NOT interconnect the hot and cold. IF it is working correctly it will completely stop ALL the flow from the faucet if EITHER side is shut off, but will NOT transfer the cold into the hot side. You either have a defective faucet, or there is some other factor at work causing your symptom.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
    New England
    A pressure-balance spool valve is a safety feature mandated by Federal regulations as one way to provide anti-scald technologies to a shower valve. It is designed to prevent a shower from getting excessively hot if the pressure on the cold supply side drops more than the hot side which might happen if someone flushed a toilet, or opened a heavy cold water use nearby. As mentioned, if it is working properly, at that valve, it would shut off the flow if the pressure on the other side dropped, not cross-over the supplies.
  6. jeffeverde

    jeffeverde Member

    Messages:
    80
    Location:
    L.A.
    All fixtures where closed
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,354
    Location:
    New England
    If a single handle faucet's cartridge is defective, if it can be left in a middle position, you could get cross-over from hot to cold. Some valves designs are more likely to enable this than others. If you turn the faucet's handle all the way to one side or the other, you may stop the cross-over. Shutting off the angle stops at the wall one at a time should help isolate which one is doing it, then, repair or replace that faucet.
  8. Gsalet

    Gsalet George the Plumber

    Messages:
    83
    Location:
    San Francisco
    Depending on the model of faucet you may have a bad check valve. Pressure balance valves using a separate balance spool like grohe, wolverine have check stops that can cause havoc when dirt prevents them from fully closing.
  9. breakinfixxin&learnin

    breakinfixxin&learnin New Member

    Messages:
    7
    Location:
    at home with the kids


    hey guys thanks for the info, i was in the midst of a major rehab project when i ran across the same problem and came to the conclusion (after major te$ting...$$ ) that the balancing valve requires an input from both sides. although nice in looks and unique in function i think from now on i will go back to old school 2/3 handle set up.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,354
    Location:
    New England
    A rremodeled system requires the new meets current codes...it is illegal to replace an old one with an old one. You can repair the old one, but not replace it without bringing the part you are remodeling with new, up to code things. It will make it tough when you decide to sell the house as well. The anti-scald features are a good safety feature, and can really save you or your family from injury.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,303
    Location:
    Cave Creek, Arizona
    The PB valve DOES require input from both sides, but WHY is that a problem when the hot and cold systems are functioning normally? It would ONLY be a factor while you are in test mode, or before the water heater is installed or turned on, and then they would NOT be using the shower anyway. It is like saying you do not like the cars with computers in them so you are only going to drive those from the 50's and 60's.
  12. jeffeverde

    jeffeverde Member

    Messages:
    80
    Location:
    L.A.
    You say that like it's a bad thing :p
  13. breakinfixxin&learnin

    breakinfixxin&learnin New Member

    Messages:
    7
    Location:
    at home with the kids
    yes all true, but i may not have been clear enough.

    i would not reuse items like an old tub valve, that sounds like asking for trouble and being in the residential home rental business reliability is very important to me.

    the valve was in test mode because there was no hot water coming out and i was able to do this because someone (previous owner/repair man) decided to run flex lines to the tub valve from the galvanized supply via shut off valves. i would upload pics but cannot reduce file size or dimensions enough.

    the scald guard is a pretty neat and safe feature and helps in liability

    and yes, despite the comforts and tech in todays cars i really miss my 76 chevy nova, only thing powered was under the hood !!!
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