Rule of Thumb for Maximum P-trap Height

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  #1  
Old 10-28-10, 08:07 AM
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Rule of Thumb for Maximum P-trap Height

Hello...
I'll be building some new (taller) vanity cabinets for an existing bathroom. They'll have an open shelf-bottom, and for cosmetic reasons I'd like to conceal the drain and supply lines in the upper cabinet.

I'll be reusing the existing Kolher Caxton undermount sinks, with a standard pop-up drain.

Aestetically, I'd like to re-locate the waste stub-out to be as high as possible. Could someone please provide me with a rule of thumb I can apply here? Something like, "the vertical distance from the sink bottom (top of the tail-piece) to the center of the waste stub-out must be x inches or more." Once I have this rule, I can finalize the dimensions for the new cabs and get busy.

Appreciate your help.
Trish
 
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Old 10-28-10, 02:08 PM
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I would not run the crown of the trap any higher then the bottom of the sink; this will depend on how short you can cut the drain mechanism.
There isn't a real measurment, they will all be different depending on the sink and mechanism.

UNDER NO CIRCUMSTANCES RUN THE PIPE WHERE THE SEAL OF THE TRAP IS ABOVE THE BOTTOM OF THE SINK, YOU WILL END UP WITH WATER STANDING IN THE SINK ALL THE TIME
 
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Old 10-29-10, 04:16 AM
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Thank you, Shacko--very helpful. Regards, T.
 
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Old 10-18-11, 11:20 AM
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I had the same question Trishglxk that this thread answered however I am running into a problem where the sink drains slower because I raised the trap up closer to the bottom of the sink than it originally was (but not above the crown) and I am also getting a persistent leak from the "inlet" connection. No matter what seal I use on the (brass) pipe coming down from the sink drain be it the plastic or rubber type seal I am still getting water wanting to leak at the top of the plastic nut. It comes up from there then runs down the side of the trap.

What am I doing wrong?

Sorry I do not have pics of install, just can't figure why it seems to be leaking from there seeing that happens after water has been sitting for a while not so much while it's flowing. Almost like pressure is pushing the water back up the pipe as where it is leaking is higher than the lowest part of the trap arm.

Any help is appreciated!

Thanks,
Dave
 
  #5  
Old 10-18-11, 06:50 PM
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The leak shouldn't have anything to do with the height of the trap - that joint should be water tight.

Have you tried replacing the p-trap? It's possible the threads were just manufactured incorrectly. Also, are you sure you're using the right size plastic washer? The trap usually comes with 2, one for 1.25" and 1.5". It's usually obvious which one to use... but just wanted to make sure.
 
  #6  
Old 10-19-11, 07:03 AM
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Thanks for the reply...

Everything I am working with is new and the threads seem okay as the nut spins on easily and tightens down good. I am using the seal that fits snug on the pipe coming down from the sink.

I just don't understand how the water is leaking there when it is just above or level with the crown of the p trap? And it doesn't start leaking immediately.....it takes a while for it to do so and it is ever so slightly. A few times now I think I have it and I come back and check it and sure enough it's wet on top of the nut and every connection above it is dry and not leaking so it's not running down from above.
 
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