Dishwasher supply line siphon?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by bork, Sep 5, 2020.

  1. bork

    bork New Member

    Joined:
    Sep 5, 2020
    Location:
    florida
    Replacing dishwasher. Three way (hot water line, sink faucet, dishwasher) valve on hot water supply is off. There is a single handle faucet on sink. Cold water valve still on. I have unhooked the water supply from dishwasher and laying on floor--little water came out. However I later found large puddle after wife used the sink cold water. Then I put end of water line up at sink level and low and behold, when cold water turned on there was some squirt out of the hot water line. I now assume that turning the valve off stops off the hot water supply but the two supply holes and tubes are not blocked off by the valve??? so I am getting water from the faucet cold water pushing/siphoning back down the hot water line? Is this reasonable or could it be a faulty hot water line valve. Dont want to replace a valve if its not the reason. Thanx for help/info
     
  2. wwhitney

    wwhitney Active Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    A single handle dual supply valve typically will have both outlets connected to each other whether the valve is on or off. A single handle faucet, if set to part hot/part cold, will cross connect hot and cold. So if there is no pressure on the hot, the cold water will travel from the supply, through the faucet, back down the hot supply, through the dual valve, and out of the open dishwasher supply line.

    Cheers, Wayne
     
    Last edited: Sep 5, 2020
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Joined:
    Feb 6, 2011
    Occupation:
    Semi-Retired
    Location:
    NW Ontario, Canada
    A single handle faucet moves on two axes. On one axis, it varies the mix from all hot to all cold. On the other (off-to-on) axis, it mixes hot and cold when the other axis is in the middle position. Probably when going from middle off to cold side on, it is crossing the middle on (mix) position.
     
  5. bork

    bork New Member

    Joined:
    Sep 5, 2020
    Location:
    florida
    Thanx for reply--saved me from changing out the valve!
     
Similar Threads: Dishwasher supply
Forum Title Date
Plumbing Forum, Professional & DIY Advice Dishwasher supply line connection Oct 14, 2020
Plumbing Forum, Professional & DIY Advice Replacing Dishwasher Water Inlet Valve - Water supply is solid copper...how much can I flex that? Dec 17, 2019
Plumbing Forum, Professional & DIY Advice Supply line question during dishwasher repair Sep 7, 2018
Plumbing Forum, Professional & DIY Advice Supply for sink + 2 Dishwashers Aug 12, 2018
Plumbing Forum, Professional & DIY Advice Water supply stub out behind dishwasher? Jan 18, 2018

Share This Page