Moen rough-in tub/shower valve questions?

Discussion in 'Shower & Bathtub Forum & Blog' started by FJK, Dec 31, 2007.

  1. FJK

    FJK New Member

    Messages:
    73
    Location:
    Illinois
    I'm confused by the terms used for Moen rough-in valves used for tub/shower faucets.
    1) What is the difference between their posi-temp pressure balance valve & the Moentrol pressure balance valve?
    2) For any valve, what do the terms cc, imt, etc mean for the type of conncection?
    3) What is the M-pact system?

    I currently have the rough-in valve that takes the small, faucet type cartridge. What I want (I think) is the type of valve that has the larger type cartridge. Specifically, I want the rough-in valve that solders to 1/2" copper, has intregal shout-off valves, & keeps shower temp constant, even if some one flushes a toliet.

    Please educate me.
    Thanks, FJK
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,129
    Location:
    New England
    A pressure balance valve would sense the reduction in pressure from the cold side and lower the hot water to compensate, reducing the ultimate volume on both feeds.

    A temperature sensitive valve needs to react to the difference in temperature caused by decreasing the cold flow, dropping in temp of the hot side, or decreased temp of the cold supply. It does this by either reducing the hot or increasing the cold, ultimately producing the same effect. It has the added benefit of adjusting the outputs automatically as you use up the hot water in the WH tank, stretching the time the temperature remains constant until it's running all hot (which may be cold by then). WIth a pressure balance valve, as you use up the hot water, you'd have to be adjusting the valve to keep the temp fairly constant since the pressure wasn't changing, the temperature(s) of the supplies are.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Positemp has a balanceing spool integral with the off on cartridge. Moentrol, the on/off cartridge is the regular moen pull out type, and the pressure balance spool is a completey separte part inside the body.

    CC of something like that means copper sweat connection, FIPS, or NPT, are references to pipe thread. Others may have connections for CPVC or PEX.


    M-pact is Moens buzzword for the system where you use a common valve body and select from a wide array of trim which fits it.
  4. FJK

    FJK New Member

    Messages:
    73
    Location:
    Illinois
    Thanks for the help, guys. I've noticed some valves have "1/4 turn stops" to control maximum hot water temperature (which I don't really need). However, aren't these 1/4 turn stops also serve as a shutoff valve, making it easy to remove the cartridge? Anyone know?
    Thanks, FJK
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    The integral 1/4 turn stops are for service. They would never be used to control temperature or water volume. On a Positemp, there is an adjustable mechanical hot limit stop, under the handle.
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