Quick (hopefully) WC to Tub drain question.

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Kenolds

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I am adding a new bathroom onto my house. I have a question about the interraction between my toilet drain and tub drain. The toilet drains into a 3" pvc horizontal (almost - sloped down at 1/8" / foot) pipe. There is a 2" vent coming off the top of this 3" drain in the wall directly behind the toilet. I then plan to combine the 1 1/2" P-trap from my tub into this 3" drain line with a 45 deg. wye fitting turned on its side. The wye will be about 6 feet downstream of the toilet. Here is my question...

1) Will the P-trap of my tub tend to get smelly by being downstream of the toilet? There will be about a 1 foot piece of pipe between the trap and the wye fitting.

If so, would it be better to let it drain into the top of the 3" main drain rather than entering into the side?
If so, is siphoning out my P-trap a concern?

THanks
-Kenolds
 

Jadnashua

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The trap is what isolates the room from the sewer, so if that is full, it is mostly irrelevant what's downstream. Now, whether the rest of the layout is correct, I think the pros would need a little more info on the actual layout. 1/8"/foot is below the recommended minimum slope (it might be okay on 4" and larger pipe), so that could be an issue.
 

Kenolds

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Glad I asked! I thought the vent between the toilet and the tub (closer to the toilet) would protect me from siphoning out that tub trap. How about entering the side or top of the 3" drain? As far as the slope goes, 1/8" per foot is what my code book says for 3" pipe. 2" gets 1/4" / foot. What slope do the pros use?

Thanks!
Kenolds
 

hj

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Kenolds

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Thanks for the advise and thanks for putting up with those of us who have limited plumbing knowledge. That's why I was very happy to find this forum. I will add the vent and run the 1 1/2 pipe from the P-trap into the side of the 3" drain with the 45 degree wye fitting. Does everyone observing think that will work?

Thanks.
 

Kenolds

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Thanks, Terry. I will follow your advice. That brings up another potential problem spot then in my plumbimg layout. I have two sinks next to each other in a double vanity. My plan is to come out ot the right sink trap with a 1 1/2 drain pipe running horizontally to the left. The left sinks trap will tee into this horizontal pipe with a long turn tee. SHortly after this tee I will have another long turn tee running vertically that will attach to a 2" vent and run down into my crawlspace where it continues on. The question that has raised in my mind is that if the tub needed that extra vent to keep from siphoning, will I need a vent between the two sinks also?

Thanks
 
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