shower/tub lower hot water pressure

Discussion in 'Shower & bathtub Forum & Blog' started by GaryD, Dec 4, 2006.

  1. GaryD

    GaryD New Member

    Messages:
    16
    I just installed a new shower/tub in the basement. The hot water has less pressure than the cold water. They both have good pressure but the hot is less than the cold.

    The shower/tub diverter has an anti scold device. Would this reduce the hot water pressure?

    I don't have this problem anywhere else in the house.

    I don't want to install the drywall if there is something I need to check or do. I haven't hooked up the sink but could connect it just to check the hot & cold pressure.
    Thanks, Gary
  2. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    When you say new do you mean replacement or additional. Did you blow out the lines B4 you tried running the water? What did you use for the water lines, copper, CPVC, PEX?
    Last edited: Dec 5, 2006
  3. GaryD

    GaryD New Member

    Messages:
    16
    It was a new (non existing) basement bathroom. I used CPVC 1/2" off the 3/4" overhead cold lines and ran 15-20' to the hot water tank to get the hot water. I did not blow the lines out before connecting or turning on the water.

    The cold water is visually 2-3 times more pressure(flow) than the hot.
  4. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    I would blow out the lines and if that doesn't help. Try running 3/4 from the heater to the bathroom and then drop to 1/2". I am assuming that you are connecting to 3/4" at the heater now?
  5. GaryD

    GaryD New Member

    Messages:
    16
    The lines I connected to are 3/4". I ran 3/4" CPVC into the new bathroom and reduced to 1/2" CPCV when I teed off for the shower and sink.

    How do I blow the lines out? What kind of stuff might be in the lines?
    Should I remove the diverter valve and check for anything?
  6. 3/4" right till the end?

    gary
    ...if I understand what you just wrote, there is VERY little length of 1/2" pipe. Is that right? I used 3/4" on all hot water lines (tub and shower), right up to the nipple that connects to the shower head or spout. No question then whether I am getting the highest quantity flow pressure and all that.

    My cold water line is reduced to 1/2" for only a few feet (to my tub), and it produces less than HALF the flow of the 3/4" which is a lot longer since it hAS to go to and through the HW tank first. In your case things are WORSE because your lines are much longer than mine were, and I think that running 3/4" for 20' is already a big drag on flow. Don't forget that the cold water has to go to and through the HW tank first, before it becomes a hot water line... So it really needs a big pipe later! Even with that, your cold water will always be at a higher pressure/ flow rate in the 3/4" pipe, since it hasn't had to go to and through the HW tank first... i repeat.

    David
    Last edited: Dec 5, 2006
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,023
    Location:
    New England
    Take the guts of the valve out and then turn the water back on. While you have the guts out, check to see if you have any crud caught either in the cartridge or on the inlet. Some valves use a screen on the inlet. The hot is more prone to crud, especially after you turn things off then repressurize the system, dislodging anything in the initial rush.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,647
    Location:
    Cave Creek, Arizona
    The balancing unit in the valve SHOULD keep the hot and cold pressures equal, because that is what a "pressure balancing spool" is supposed to do.
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