Cross Connection

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by malder, Sep 13, 2005.

  1. malder

    malder New Member

    Messages:
    5
    How do you trace a cross connection? Do you do it purely by trial and error?

    I've attached an image of the general layout of the house, hopefully you can help me solve this faster than I would otherswise.

    The faucet on the basin sink gets piping hot on the cold side and hot side fairly quickly. As soon as I shut the WH valve off it gets cold... cross connected right? The further the fixture is from the water heater the colder the cold side is, but never as the same temp as when the WH is shut off.

    The only single handle fixture is the kitchen faucet, which I turned off, with no difference.

    Any ideas on where to start?

    Thanks

    Attached Files:

  2. Check to see if the washing machine solenoid valve is in the open position, see if a hose has been attached to the laundry tub faucet with an attachment on the end of the hose. These are the two most common cross-connections from cold to hot. If any work has been done (plumbing) in the home this might be the culprit as well.
  3. malder

    malder New Member

    Messages:
    5
    forgot to mention: No plumbing work has been done for 2-3 years. Problem has developed over the last ~2 months
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,056
    Location:
    Cave Creek, Arizona
    Washing machine valves cannot cause a cross connection. Turn off the valve to the water heater and then open a hot water faucet. If there is no flow there is no cross connection. If there is flow, then leave the faucet open and check all the other faucets. You may be able to hear water flowing through one if it is bypassing.
  5. plumber1

    plumber1 Plumber

    Messages:
    1,423
    Location:
    Florida
    water

    Or just close the hot or cold supply to the washer, then check.
  6. malder

    malder New Member

    Messages:
    5
    I let the wash basin faucet get nice and warm (on the cold side :( ) and then turned the WH valve off. Pretty much instantly the water turned to normal temp. That screams cross connection, no?

    thanks for the responses.


  7. Yes they can. If a washing machine is unplugged while in the fill mode, the solenoid can sometimes remain open (or malfunctioning). Or just mechanical failure. Usually more than one fixture is affected though. Not a common thing but as plumber1 stated, shutting off the valves that serve the washing machine is recommended to rule that theory out.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,056
    Location:
    Cave Creek, Arizona
    valve

    IT still cannot happen because the valves are pilot operated and will not stay open, but even if they did the outlets for the two valves just dump into a funnel going into the machines's tub and there is no way for that to build up any back pressure at all, much less permit the two systems to mix. in order to mix, there would have to be a third valve between the two inlets and the tub, and no machine has that.
  9. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    In a cross connect situation it is more common for cold water to flow back to the hot side. This is due to relative differential pressure.

    What you describe sounds like a check valve failure in a pumped recirculation system. Do you have recirc?

    By the way, hj is completely correct about the washing machine solenoid valve. Although striclty speaking the H and C mix inside the valve, they mix in an outlet which is very close to atmospheric pressure, so from a practical standpoint, there can be no crossover between supplies.
  10. malder

    malder New Member

    Messages:
    5
    there is no recirc on the system. Everything is pretty old, so unless they hid the pump out of sight then there isn't one

    Thanks for the help. I have a feeling this may be a tough one to nail. :confused:
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,056
    Location:
    Cave Creek, Arizona
    cross

    It is only difficult because you are there and we are here. If we were there, it would probably be a matter of minutes to pin it down, since there are only a couple of tests to see if you have one, and then very few places it could occur.
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