Moving P-Trap from Below the Floor to Above the Floor

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pcantin

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Hello to you all.

I am putting in a new double basin kitchen sink and want to use new pipes for the drain. Currently, the p-trap is under the floor (see diagram for the present setup). Is there an advantage to putting the p-trap just below the sink instead of having it below the floor? The vent needs to stay where it currently is. It is an open basement ceiling, so the p-trap is accessible no matter the configuration.

If I can set up the trap above the floor, how long must the pipe be from the trap before dropping vertically (the green section on the image) and how far down can it drop vertically after the trap and before the vent (the red section on the image)?

p-trap.jpg


I will most likely keep the setup as is since it drains well with no odour. Just wanting to know if there is any advantage to changing it.

Thanks for your help on this (I am in Ontario).
 

Jeff H Young

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why are you changing it ? America the p trap is always above the floor 100 percent of time but your in Canada no idea why we are diferant
 

pcantin

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why are you changing it ? America the p trap is always above the floor 100 percent of time but your in Canada no idea why we are diferant
Just redoing the plumbing that is poorly done to clean it up a bit (dishwasher wye is cracked, etc.). I figured I would see which configuration is better now that I will be re-plumbing it. Yes, we are permitted to have the trap below the floor (we can go 36" down from the sink before the trap if I am not mistaken).

I am pretty sure I will recreate what is already there, as it did drain well.
 

wwhitney

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If I can set up the trap above the floor, how long must the pipe be from the trap before dropping vertically (the green section on the image) and how far down can it drop vertically after the trap and before the vent (the red section on the image)?
For the last question, the answer is one trap pipe diameter. So for a 1-1/2" trap, it can drop 1-1/2" at most.

In other words, you'd need to move the vent connection to above the floor. If your jurisdiction allows AAV, that would be one option to do that.

Cheers, Wayne
 

pcantin

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Thanks for the replies. I think it will be easier to keep it as is. Again, it drains quickly and without issue, and it did pass inspection when it was put in.

Much appreciated!
 

Jeff H Young

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Thanks for the replies. I think it will be easier to keep it as is. Again, it drains quickly and without issue, and it did pass inspection when it was put in.

Much appreciated!
I wouldnt give much credit for passing inspection Inspectors are no better or worse than tradesmen really they miss stuff
 
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