Proper drainage of a bathtub

Discussion in 'Shower & bathtub Forum & Blog' started by bholder, Jul 23, 2007.

  1. bholder

    bholder New Member

    Messages:
    17
    Hi everyone, I'm from St. Louis MO. Got a drainage issue with a bathtub. The previous owner put the drain on the wrong side (left side) for a shower to work. I have installed a brand new tub on the right side but have come up with an issue. My drainage plumbing runs underneath the length of my tub and connects to the old plumbing.
    The problem is that the 1-1/2 inch plastic plumbing running underneath the tub runs level with the tub to make the connection with the existing plumbing. I do not have the required 1/4 in drop per ft. and I don't think I can get it since the existing plumbing is even with my plumbing and then disappears down into the wall where I can't get to. When I run the shower to test I'm getting about a 1 inch deep puddle of water per 15 minutes of shower time. Once the 15 minute shower is over, the water does quickly go down the drain. Do I have a problem or should I live with it? This is a guest bathroom so it won't get very much use.
    -Thanks for any help you can provide.
  2. good enough, for now. Not good. What to fix, change, improve on ... only one right way which involves total replumbing. Other fixes merely reduce the symptoms of the true problem.

    Overall your description may be clear enough for me to get the entire picture, accurately. I guess you have both a shower and a tub, and the tub drain goes under the 5' length of the tub to connect to a vented stack but not before combining with the shower drain first. Is that right?

    david
  3. bholder

    bholder New Member

    Messages:
    17
    drainage problem

    Thanks for your response David and your help. I have just a bathtub hooked to the line, no second shower. The showerhead is part of the tub system. I'm assuming my tub will be used 99% of the time for taking showers, not baths. I've included a pic of my rubber boot connection at the far end of the tub that connects my new pvc plumbing line to the old copper line. I left the old copper p-trap in and connected to that. You can see where the joist had been previously cut, but only about an inch out of a 2x10. The pic is looking straight down at the connection. I had to make this pvc u-loop to get the plumbing going in the right direction to make the connection. The problem is even if I cut out the old copper p-trap in the left hand side of the pic the connection is still level with my new pvc pipe. I can't get any slope. Now what do I do?
    I also included a pic of the pop-up drain. I'm also wondering if drains like this might be notorious for causing puddling because they just don't drain fast enough.

    Attached Files:

  4. bholder

    bholder New Member

    Messages:
    17
    drainage problem #2

    Just to clarify: I have a new p-trap at the head of the tub that I installed and I left the old copper p-trap in at the end of the tub. That may be a factor too. I've got 2 p-traps going on.
  5. diagnosis; partial diagnosis.

    glad you mentioned that. It all adds up.

    if i got it right, based on what may be complete disclosure,
    you have
    A.) both these things,
    - 1.) a new white plastic (PVC) P trap under the tub drain, and
    - 2.) you left in the drain line an old copper P trap under the subfloor,
    so
    B.) your drain water goes through both these P traps,
    and furthermore
    C.) you routed the pipes to catch the angle of that old copper pipe (P trap) using a number of quarter bends.



    is that the right picture in my mind?



    David
    p.s. the chrome thingie (pop up) and its mechanism is not the problem. 100 million of them out there and counting.
  6. bholder

    bholder New Member

    Messages:
    17
    plumbing problem

    David,
    Yeah, you got the pictue. I think you are hinting that I've got too many angles in the pipes and maybe I should work on making a straighter line of flow for the water to run. I would agree, but still, even if I eliminate the pvc u-bend and the copper p-trap and connect directly to the drain, it will still flow horizontially since the copper drain is at the same height as my pvc drain.
    Someone mentioned on this board about filling the tub up and then letting it drain to see how long it takes the water to go down. What is the general rule of thumb on how fast it should drain?
    I wish I had a benchmark of what is acceptable drainage for a tub.
  7. quiz: what's the problem? Is there only one big one? Are there a lot of small ones? Are they independent, or do they interact, inter-relate, cause dependencies? You have an unusual set of problems. Since you are online and i am too, stay tuned just a little bit longer. Plumbing can be fun.

    brainstorming...
    - benchmark tub drain?
    - remove bends and that second trap?
    - do you really have no drop from before and after that second trap?
    - remove first trap?
    - add AAV at first trap?
    - resolder copper trap so it's oriented to receive a straight PVC pipe?

    David
  8. bholder

    bholder New Member

    Messages:
    17
    Drainage problem

    To help I've drawn a crude illustration of my problem as an attchement. I hope this helps in the diagnosis.

    Attached Files:

  9. bholder

    bholder New Member

    Messages:
    17
    Benchmark

    Actually any guidance on a benchmark on how fast a tub should drain would be really helpful. Maybe I'm just making a mountain out of a molehill? Maybe my connections are good? The tub does drain properly and reasonably fast. If I run the shower full blast for 15 minutes with the drain wide open I get about 1 inch of waterbuildup. Is that an acceptable amount?
    It seems that I stayed at a hotel about a year ago that the tub was almost 4-6 inches of waterbuildup after my 15 minute shower. Maybe I'm in an acceptable range?
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,949
    Location:
    New England
    A typical tub filler is in the order of maybe 6gpm with 1/2" supply lines. A showerhead is restricted to a 2.5gpm max. My tub doesn't back up running the tub filler at max and would not have any trouble keeping up with the showerhead. You really need to get rid of the second p-trap. At the same time, you might be able to lower where it connects to the trap giving you some slope. Make gravity work for you. My big tub that takes maybe 7 minutes to fill, empties in about 2.5; that's about 18gpm into 1.5" drain.
  11. very good ! The next thing to consider is the level (height) of these P traps.

    Your original question was about what is proper ("Proper drainage..."). The second P trap was probably at the right height for it to connect "properly" to the vented stack that is (may) behind the wall.


    This is key. This is the core of the problem. The height of the pipe coming out of the P trap is the one thing to watch to avoid a bunch of other problems that you don't have. Yet.



    Diagnosis ::
    A.) -- your original P trap was (probably) OK. Its height was (probably) OK.
    B.) -- you can only have one P trap in series.
    C.) -- a straight drain pipe is best.




    Solution - Alternative 1. :: work with copper and soldering, to undo and reconfigure the P trap's angles, only to rotate the pieces. Doing so won't change their height since the pieces all fit back together at that height. Connect the P trap to a straight PVC pipe.

    This is not optimal since you have a long pipe before the P trap.



    Solution - Alternative 2. :: place that P trap (or a new one, e.g. made of PVC) directly under the tub, low enough down that you get the P trap's outlet (tailpiece) to be at the right height so that its long long tailpiece ends up at the right height when it reaches its connection going into the wall.

    This may be best. The drop from the tub to the P trap won't be too much. Is there a room (living space, ceiling) that it would interfere with?



    Solution - Alternative 3. :: AAV - not to be considered, for now.




    David
  12. bholder

    bholder New Member

    Messages:
    17
    drainage problems

    brainstorming...
    - benchmark tub drain?
    Yeah, maybe I'm making too big of a deal on this and I've got an acceptable drainage?
    - remove bends and that second trap?
    Do you think my second trap is a problem, possibly slowing down my drainage too much?
    - do you really have no drop from before and after that second trap?
    It looks pretty even to me. if the run is 5 ft and I need a 1/4 inch drop per foot I know it isn't sloping down 1-1/4 inches where it meets the copper pipe connection.
    - remove first trap?
    I'd hate to have to remove the first p-trap. I did such a good job on it!
    - add AAV at first trap?
    Not sure what an AAV is.
    - resolder copper trap so it's oriented to receive a straight PVC pipe?
    I could simply cut it off and eliminate the copper p-trap.
  13. since it is not at the right height, it has to be cut and repositioned lower. Then you get the right slope down to the wall connection.

    1/4" per foot slope. Pipe a straight line or an offset - that's a slight zigzag shape.

    David
  14. bholder

    bholder New Member

    Messages:
    17
    drainage problem

    Jim's advice was helpful too. I'm at work now, but when I get home I'll fill the tub up and see if I can get it to drain out in 2 to 4 minutes. Maybe that is a good indicator if I've got a problem?
  15. both P traps wrong.

    In other words, both your P traps are in the wrong place, or not configured right.

    David
  16. no, you have a problem, regardless of the benchmarking test results. Forget this subject. Forget benchmarking. You are past it already; that is why i spent time on "brainstorming" ---just to give you a sense of the bigger picture. The question is not "maybe i do maybe i don't, and what might it be..."

    I'll step out now and let other people confirm the analysis.

    David
    Last edited: Jul 24, 2007
  17. bholder

    bholder New Member

    Messages:
    17
    drainage.

    Are you saying get rid of the p-trap located directly under the tub or get rid of the old p-trap located at the back of the tub? The old copper p-trap would be the easiest to eliminate. Maybe I could get a slight slope then.
  18. using a tool called a level, you can determine if you have enough height to make the slope.

    When I posted about 90 minutes ago spelling out a couple alternatives, I thought you'd have plenty of slope. Guess not.

    david
    Last edited: Jul 24, 2007
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,949
    Location:
    New England
    get rid of the old p-trap. This may allow you to run the pipe at the proper slope back to the stack. If you have room where it makes the connection into the stack, consider redoing that whole fitting and connection. At the least, cut off the old p-trap, and see if you can find the proper no-hub connector to attach to your new run. Having the p-trap in the wrong connection (i.e., not right under the tub drain) will eventually smell raunchy from accumulated crud in that long pipe. the water int he p-trap essentially cuts that off at the water level.
  20. bholder

    bholder New Member

    Messages:
    17
    proper drainag

    OK guys, that sounds good. I'm going to cut out my rigged u-trap configuration, cut out the old copper p-trap configuration and try to tie the line straight into the pipe. No more twists and turns. I'll leave the p-trap under the tub drain which should be correct. Hopefully there will be some sort of acceptable slant to get some drainage. I'll let you know how it works in a few days with some pics!
    -thanks guys for your help!
    Last edited: Jul 24, 2007
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