no cold water when water heater shut off

Discussion in 'Shower & Bathtub Forum & Blog' started by mountain-top mike, May 4, 2014.

  1. mountain-top mike

    mountain-top mike New Member

    Messages:
    12
    Location:
    Lake Arrowhead California
    I have not seen this issue addressed before so I will post here. Was working at a house yesterday servicing water heater.I shut it off at inlet and was cleaning it when the owner said that no cold water was coming out of any shower fixtures. All valves are moen single handle, no posi-temp. The lavatories are fine with 2 handles. The kitchen single handle Blanco has cold running from it. I have never really seen this issue come up. Water heater buttoned up and all is normal. I am guessing that is the way the valves operate?
  2. Smooky

    Smooky Member

    Messages:
    629
    Location:
    NC
    Some anti-scald shower valves are designed to do that.
    Last edited: May 4, 2014
  3. mountain-top mike

    mountain-top mike New Member

    Messages:
    12
    Location:
    Lake Arrowhead California
    These are moen valves and I assume that they are anti-scald? Since the kitchen faucet isn't anti-scald the cold would work there. Thank's Smooky.
  4. mountain-top mike

    mountain-top mike New Member

    Messages:
    12
    Location:
    Lake Arrowhead California
    What prevents the cold water from exiting the valve? When the valve passes over the cold port shouldn't some water come out?
  5. Smooky

    Smooky Member

    Messages:
    629
    Location:
    NC
    On a mixing valve such as at the kitchen sink you turn on the hot and the cold water and you get warm. If you shut off the cold you only get hot water. Anti-scald shower valves are designed if the cold water is turned down, only a small amount of hot water will come out. That way if you are in the shower and someone flushes the toilet you do not get a blast of hot water. With that type of shower faucet if the cold is shut off completely then the hot will not come out either.



    About 11 minutes into this video he has a cut away valve and he does a good job of explaining how it works: https://www.youtube.com/watch?v=d2hpPmgsS_o
    Last edited: May 4, 2014
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,268
    Location:
    New England
    Many of the systems use what is called a spool valve - when water pressure is present on both sides (one has hot on it, the other side has cold), the spool valve is centered, and all works fine. If the pressure on one side drops, the spool valve slides towards the lower pressure side and that slows, or in extreme cases, shuts off all flow out of the valve - in effect, trying to maintain the balance of hot/cold coming out. When the valves start to get old, shutting off one supply and jamming the spool valve to the other end and literally jam it in position (the seals may be getting hard, or there's some crud in there or who knows), and the only way to restore proper operation is to either remove and clean (not possible on many) or replace the spool valve assembly (which is inside some cartridges, and separate in other designs). Once in awhile, you can give it a good rap with a mallet, and it might free up, but it's an indication you might want to consider replacing it.
  7. mountain-top mike

    mountain-top mike New Member

    Messages:
    12
    Location:
    Lake Arrowhead California
    Smooky, that makes perfect sense. If the pressure is out of balance, so to speak, then the valve goes into kind of a shut down mode. And the reverse is true that if the hot water is shut down the cold also stops so one does not get an arctic blast of water!! All of the 6 shower and tub valves do this and they are new so they are working correctly. Explained this to the owner and he understood how the system works. I will look at the video a little later when chores are done. Thank you Smooky and jad.
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