mixer rough in?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by scott99, Feb 4, 2007.

  1. scott99

    scott99 New Member

    Feb 1, 2007
    I'm about to rough in my new shower mixer and was planning on coming from my hot and cold feeds via 90 degree elbow to the mixer. I noticed on my old valve they connected it via tees instead of elbows and the top connection of the tee was just connected to about a 8inch pipe then capped.

    was this for expansion to control water hammer and should I plumb my new mixer in the same way?
  2. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    Yes, the 8" piece was an air chamber. Good theory, doesn't work, because from natural turbulence in the pipes, it just fills with water quickly.

    If you have an issue with water hammer, get a commercially available hammer arrestor, which use a bladder.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    air chambers

    The longer the air chamber is, and the larger the pipe diameter, the longer it will be before it becomes waterlogged, but it will happen eventually. And once it does there is no practical way to regenerate it.
  5. srdenny

    srdenny Plumbing Contractor

    Sep 11, 2004
    Plumbing Contractor
    SF Peninsula
    "And once it does there is no practical way to regenerate it..."
    other then shutting off the water, draining the system and turning it on again.
  6. kordts

    kordts In the Trades

    Oct 15, 2005
    industrial service plumbing foreman
    exurban Chicago
    Usually there is a vacuum that prevents the airchamber from draining.
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