Additional knob/valve inside shower wall

Discussion in 'Shower & bathtub Forum & Blog' started by JohnNJS, Nov 21, 2012.

  1. JohnNJS

    JohnNJS New Member

    Messages:
    3
    Location:
    pasadena, ca
    Hi,
    First time posting in the forum - hope i get it right. I'm a plumbing novice and am not sure what the additional knob below my shower handle stem is. I've been trying to find out via the internet but it's difficult because i don't know what to search for. Most pictures of two-handle system (e.g. here http://www.diyadvice.com/diy/plumbing/faucets/tub-shower-stem-compression/) do not show the lower knob or valve.

    I'm assuming it is, or was (my construction is original 1971) common as these tear-drop escutcheons are something i've seen a lot and I assume were intended to disguise this additional part. However that is as far as my deduction has taken me.

    Has anyone seen this part? What does it do? I thank you in advance.

    small.jpg

    Attached Files:

  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,815
    Location:
    NW Ontario, Canada
    My guess is they are integral shutoffs so that you can work on it without having to turn off the entire house.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,773
    Location:
    New England
    Well, an integral set of shutoffs would be that, a set, and there's only one!

    If I had to guess (I'm not familiar with many different ones), it might be either the spool pressure balance valve, or it's a max temp adjustment.
  4. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,132
    Location:
    South*East
    The one your looking at is on the cold side. The second one would be on the hot side. It's a two valve shower valve.

    John
  5. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,815
    Location:
    NW Ontario, Canada
    I reject your reality and substitute my own.
  6. JohnNJS

    JohnNJS New Member

    Messages:
    3
    Location:
    pasadena, ca
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,173
    Location:
    Cave Creek, Arizona
    They usually snap the slotted head when you try to turn them. Usually completly useless after a few years.
  8. JohnNJS

    JohnNJS New Member

    Messages:
    3
    Location:
    pasadena, ca
    Oh no! Bad news. Thank you for letting me know. Do you know if, when that happens, it creates disaster (i.e. water spraying out)?

    Also, any use spraying on some penetrating oil or something on it before I try it out?
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