Bath Sink PTrap Options ..

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by beachfront71, Sep 28, 2011.

  1. beachfront71

    beachfront71 New Member

    Messages:
    43
    Location:
    newport beach, ca
    Hi and thanks.

    We are dropping 2 vessel sinks on top of an old dresser we had refinished.

    In order to try and conserve/use as much of the drawer space below the sinks I was loooking for some answers to the following:

    1. Is there a minimum distance a ptrap should be below the drain hole of the sink?

    2. Could I run the drain down 5 inches then elbow towards the wall, then put the ptrap in and go down to the ABS stub?

    Any other suggestions appreciated! Using 1.5 compression fittings from home depot if it matters..

    BTW. All of this will be inspected by the city.

    Thanks again for any and all time spent/
  2. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,626
    Location:
    Cave Creek, Arizona
    Your quetion #2 would create an "S" trap which would NOT be approved by the city. The "ADA" drain will NOT have a stopper or popup drain and would NOT normally be suitable for a bathroom fixture, besides usually only being available in Chrome finish. If your vessel sinks do NOT have overflow openings, then HOW you connect from the sink to the trap will have a lot to do with how well they drain.
  4. beachfront71

    beachfront71 New Member

    Messages:
    43
    Location:
    newport beach, ca
    Thanks for the info ..

    And yes, the sinks do have an overflow on them. and we do have pop up drains ..

    How far down does the drain need to go before adding the ptrap?

    If this distance is minimal and I can put the ptrap close to the sink, then run everything back to the wall then down and out .. that works!

    THanks again.
  5. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,973
    Location:
    NW Ontario, Canada
    Can you raise the ABS stub out?
  6. jastori

    jastori New Member

    Messages:
    118
    Location:
    Illinois
    There is no minimum vertical distance between the drain in the sink and the start of the p-trap. Usually, the vertical section directly below the drain is needed to accommodate the pop-up drain mechanism (open/closed). If you don't care about a pop-up mechanism, you can offset horizontally directly below the drain closer to the wall, and then drop into the p-trap - that is how the ADA drain would work. This is also similar to what happens under a bath tub.

    The key issue that the other posts are referring to is the vertical height of the connection after the p-trap. You cannot drop vertically after the p-trap until you connect to the vent. If you do, you effectively create an 's-trap', which can cause drain problems, including siphoning of the trap. This is why there is a suggestion to 'raise the stub-out'. Raising the stub-out means opening up the wall and cutting pipes, and moving the fitting up higher to the proper height for the p-trap exit.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,003
    Location:
    New England
    Also consider that the longer the piping is before it gets to the trap means more length of pipe that can get crud accumulated in it to start to smell. The trap, filled with water, masks any smells that may be there beyond that connection.
  8. beachfront71

    beachfront71 New Member

    Messages:
    43
    Location:
    newport beach, ca
    Thanks for all of this and the explanations .. makes total sense ...

    Last question -- if this does not work than I am doing the normal down to ptrap across to ABS...

    So from the sink drain .... Could I

    1. Down 4 inches to an elbow
    2. from elbow, back towards wall 10 inches to another elbow pointed down
    3. now go down 12 inches into ptrap
    4. from ptrap directly/horizontal to wall (3 inches)

    This gives me all the room I need and lets the overflow drain pop up .... just want to make sure I can go horizontal and vertical before ptrap .... only horizontal after...
    Last edited: Sep 29, 2011
  9. jastori

    jastori New Member

    Messages:
    118
    Location:
    Illinois
    Yes, that should be fine. Your 'horizontal' section should still have a small slope - you don't want water sitting there. Jim mentioned the downside of the extra pipe before the trap. Worst-case would be that you need to take it apart and clean it at some point. If you are not happy with it long term, it is always easy to convert back to the 'standard' install (p trap directly below the drain).
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