Supply for sink + 2 Dishwashers

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by MNorA, Aug 12, 2018.

  1. MNorA

    MNorA New Member

    Aug 12, 2018
    We are in the middle of planning for a kitchen remodel. We have an island sink and the boss decided she wants 2 dishwashers added to the island, one on each side of the sink. Can we tee off the existing hot/cold 3/8" supply lines to both dishwashers? Would there be enough water pressure for sink + 2 dishwashers? Anything else to consider?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    I wouldn't want to try to use a 3/8" line to feed two DW and a sink...while the DW probably have a float or level control and might just fill slower (and extend the wash cycle time), if one or both of them were on and you wanted to use the sink, the flows would be pretty pathetic. FWIW, the copper institute's recommendation for maximum velocity of hot water in a pipe is 5fps, and a 1/2" pipe would equate to 4gpm. Because of the squared factor of the area, dropping to 3/8" would end up about half of that. A kitchen faucet is flow restricted, and just about maxes out a 3/8" line on hot...throw in two DW, and it won't work well. I'd want to feed things with a 3/4" line, then tee off to the three devices using smaller pipe/hoses.

    Last edited by a moderator: May 27, 2020
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  4. plumber69

    plumber69 In the Trades

    Jun 20, 2014
    Prince Rupert, British Columbia
    If your in the middle of a remodel wouldn't you be opening up your island where the water lines are. If you have half inch copper for your hot line you will be fine. I would stub out 3 hot lines. Not likely you will be using the faucet if both dishwashers are running. And I dought you would start them at the exact same time.
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