3 handle valve to single handle valve question.

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by cdubya, Feb 8, 2009.

  1. cdubya

    cdubya New Member

    Messages:
    18
    Location:
    little rock
    I have a 3 handle valve in a tiled tub/shower and want to update to a single handle valve. The existing drop from valve to tub spout is only about 5" and Delta calls for an 8" drop. If I move the valve up to create the proper drop, the adapter plate won't cover the 3 handle holes in the tile. Is there a way to compensate for the less than minimum drop that is reliable/legit?
  2. I've set countless valves without that minimum without error or callback, but I prefer to follow mfg. specs whenever possible.


    The piping between the tub spout and the showerhead must be copper piping.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,508
    Location:
    Cave Creek, Arizona
    valve

    That 6" dimension was decided upon by an engineer who had absolutely no idea why it had to be that way. Maybe because he read some book published in 1940 that specified that dimension. If the trim ring on the new valve does not hit the spout, do it the way you have to.
  4. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    Just guessing, but if you're using something based on Delta's "universal" valve, that spec may be to cover any possible trim they may intoduce at some time unknown, which could include trims that need that much space to avoid the handle trim meeting the tub spout.
  5. cdubya

    cdubya New Member

    Messages:
    18
    Location:
    little rock
    Thanks for the comments. Delta said the 8" minimum drop is so water won't back up and dribble out the shower head when filling the tub. If the 5" drop isn't enough, I've wasted time & money on a new valve. The old tile can't be matched to patch existing holes if I move the single handle valve up. What do I do if I get the dribble on the 5" drop?
  6. kingsotall

    kingsotall Plunger/TurdPuncher

    You'll have an understanding of why it does that and maybe could possibly live with it. Some people call these things giving a house character.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,508
    Location:
    Cave Creek, Arizona
    dribble

    You might get a "dribble" if the pipe were LONGER than 8", but almost impossible when it is less. The dribble is caused by back pressure and the longer, or smaller diameter, the drop the more back pressure is created.
  8. cdubya

    cdubya New Member

    Messages:
    18
    Location:
    little rock
    Apparently, Delta agrees the drop can be too much. They advise the drop from valve to spout be 8"-18" to avoid "shower-rise". First, I've got to figure out if the cover plate will fit above the new spout and still cover the existing holes. Even with your encouraging comments, it feels like a leap of faith with the existing drop being so far outside the recommended range.
  9. Terry

    Terry Administrator Staff Member

    Messages:
    14,904
    Location:
    Bothell, Washington
    If the tub spout doesn't hit the "pie pan" you should be fine.

    It's a common replacement for us plumbers.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,508
    Location:
    Cave Creek, Arizona
    drop

    You are placing "way, way" too much faith in the intelligence of an engineer. They deal in theory which they seldom test. We deal in actuality which we test daily.
  11. cdubya

    cdubya New Member

    Messages:
    18
    Location:
    little rock
    I like your conviction. I need to check for the clearance issue and go from there.
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