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

  1. #1

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

    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. #2
    In the Trades Jerome2877's Avatar
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    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.

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    Plumber jimbo's Avatar
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    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.

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    Moderator & Master Plumber hj's Avatar
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    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.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6

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    Quote Originally Posted by jimbo View Post
    . . . In your case, cold water crossed over and back-fed the hot piping.
    All fixtures where closed

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    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    George the Plumber Gsalet's Avatar
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    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.

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    DIY Junior Member breakinfixxin&learnin's Avatar
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    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. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by breakinfixxin&learnin View Post

    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.
    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Moderator & Master Plumber hj's Avatar
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    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. #12

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    Quote Originally Posted by hj View Post
    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.
    You say that like it's a bad thing

  13. #13
    DIY Junior Member breakinfixxin&learnin's Avatar
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    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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