Supply needed for 2 shower valves

Discussion in 'Shower & bathtub Forum & Blog' started by kingcledus, Feb 8, 2006.

  1. kingcledus

    kingcledus New Member

    Messages:
    8
    I'm in the middle of remodeling my master bath. We are installing a 5' walk-in shower and I had my heart set on installing two posi-temp Moen valves and two shower heads. I found the water supply to the bathroom is only 1/2" copper.

    Will this have the capacity to use both shower valves at the same time? I don't mind a slight loss of pressure when using both so long as they function properly.
  2. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    Your performance will not be what your looking for/expecting if all you have is 1/2 " feeding them, if they are used at the same time. Can you change the line from the water heater to 3/4"? If you can feed each valve seperately off the 3/4" line. Is the line feeding the water heater 3/4" also?
  3. plumber1

    plumber1 Plumber

    Messages:
    1,423
    Location:
    Florida
    I agree with Cass. I think he is saying that you need "volume". But if you have high pressure, that will get you more water to each.

    But if you re-pipe, it's the best thing to do......
  4. kingcledus

    kingcledus New Member

    Messages:
    8
    Thanks for your thoughts. That is what I was afraid of. It is a second story bathroom, and the water heater is in the basement, so repiping will be more of a challenge than I care to take on for this house.
  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    They should function properly and it is possible that you would get satisfactory performance.

    Shower valves are supposed to be limited to 2.5 GPM so two of them will be using 5 GPM, unless you get rid of the flow limiter.

    Pressure drop for 1/2" type M copper is 0.13 psi/ft at 5 GPM, so in 40 ft and adding a bit for losses at elbows, you might lose 7 psi.
    http://www.piping-toolbox.com/pressure-loss-copper-pipes-d_930.html

    If you keep your water heater set at a higher temperature, such as 140 F, you will be mixing some cold with the hot so the flow through the hot water line will be reduced.

    You don't say what your water pressure is. If you are on a municipal system it might be high enough that the loss in the pipe won't matter.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,005
    Location:
    New England
    Did you look at the Grohe Freehander? http://www.freehander.net/ It would simplify installation (one valve, unless you want to both be in there with your own at the same time).
  7. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I would check the post 3 down from this one about : "hot water puzzle". I suggested that 2 pressure balanced valves plumbed together might be fighting each other. That poster has requested feedback from Price Pfister on the issue. Results should be informative.
    Last edited: Feb 8, 2006
  8. kingcledus

    kingcledus New Member

    Messages:
    8
    Thanks for all the help. This site is great.

    I have not had my water pressure checked, but I would rate is as good. The risk of it not working correctly using one supply has made me decided against the two valves on one supply. There is a second half inch supply on the other side of the bathroom from the small shower I ripped out that I am going to use for another vanity. It looks to me near impossilble to branch it across the room to use for a second shower valve, but I am going to get a plummer to look at it.
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