Drain for vanity in roughed in basement bathroom

[sundevil77]

Hello, I am seeking guidance on how I should run a drain pipe to the proposed location of the vanity. I have attached a PDF that contains a few pictures of what I am thinking 'might' work. But clearly that is what I am seeking guidance on from folks who are experienced.

Thanks,
Ryan

 

[MicEd69]

The 3" vertical that you plan to use as the sink drain appears to be your main waste stack. There are different kinds of "tee fittings", and the one you show is a Sanitary tee. That is usually used for horizontal to vertical drain connections and can be used there. However, as that is your main waste stack, you will need a separate vent for the sink P-trap. It appears that the line to the left in your picture is a vent line. Just confirm that and you can run a vent line from your sink P-trap over to it. The vent line needs to be vertical, or no more than 45 degrees off vertical, until it reaches 6" above the flood rim of the sink. Then it can be run at a slope of 1/4" per foot. And since the drain connection to the stack doesn't need to be used as a vent, it would be better to use a wye or a combo fitting for the drain connection. For the vent connection, you can use any tee fitting.

 

[Twowaxhack]

I’d cut a tee into the stack on the left.

 

[Rossando]

How are you thinking about running the vent pipe?

 

[sundevil77]

The 3" vertical that you plan to use as the sink drain appears to be your main waste stack. There are different kinds of "tee fittings", and the one you show is a Sanitary tee. That is usually used for horizontal to vertical drain connections and can be used there. However, as that is your main waste stack, you will need a separate vent for the sink P-trap. It appears that the line to the left in your picture is a vent line. Just confirm that and you can run a vent line from your sink P-trap over to it. The vent line needs to be vertical, or no more than 45 degrees off vertical, until it reaches 6" above the flood rim of the sink. Then it can be run at a slope of 1/4" per foot. And since the drain connection to the stack doesn't need to be used as a vent, it would be better to use a wye or a combo fitting for the drain connection. For the vent connection, you can use any tee fitting.

Thank you. Dumb question - how do I confirm that is a vent (2" PVC) ? I would assume it is.....there is another 3" stack on an adjacent wall as well, which I know is another drain for 2nd story of house. Anyways, revised sketch attached based on your advice. Let me know if that looks good. Greatly appreciate the insight.
I also have posed a water line/PEX question on the third page of the revised sketch. Thanks again.

 

[MicEd69]

A vent will not have any drains flowing into it. It's only purpose it to allow air in and out of the drain lines to prevent siphoning of traps and assure good drainage from fixtures. You need to trace the line and verify that no fixtures drain into it. It may tie into the main vent stack in the attic, that portion of the main stack above where the last drain connection is to the main stack.

The "3-way elbow" you show is NOT and acceptable plumbing fitting and should not be used.

But as Twowaxhack suggested, if that is a vent line, you can simply use it for the sink drain. If the sink is close enough to that vent line, the sink will be properly vented if you use Sanitary tee for the drain connection and you slope the drain line at 1/4" per foot. Sink drains are usually 1 1/2", so you could reduce the drain to that, again provided you are close enough to the vent. And not that the line will still serve as a vent for downstream fixtures even with the sink draining into it.

Re: the PEX question, provided you have the space and length available to tee into the 3/4" PEX, sure. Not knowing your entire plumbing layout, you may have issues of reducing flows to some fixtures when a toilet is flushed, but I wouldn't think it would be super bad.

 

[sundevil77]

Got it, thanks for the education. It appears to indeed be a vent; will validate. Revised sketch attached along with floor plan.

Regarding PEX, will just get 1/2 PEX to run to shower, toilet and vanity to ensure no issues based on your comment. Thank you.

 

[MicEd69]

I think you are too far from the stack to vent the sink through the drain line.


I think you are under UPC, so the distance between the trap weir and the vent connection for a 1 1/2" drain line cannot be more than 3 1/2 feet. And for a 2" drain, it cannot be more than 5 feet, regardless of what the above drawing shows, which is based on IPC. IPC would allow 6 feet distance between the trap weir and the vent connection for a 1 1/2" drain line, but I think you are too far away even if you were under IPC. As such, you will need to do something like the sketch below. You need a Sanitary tee for the drain connection to the vent stack. Some people, like me, interpret that you can use a Sanitary tee on its back for a dry vent connection to a drain line, and that is what I show on the sketch below. However, some plumbers and inspectors require that connection to be a combo fitting or a wye and a 45. The fitting for the dry portion of the vent to the vent stack can be any plumbing tee, but usually they are Sanitary tees or a combo/wye + 45.



Re: the PEX question, I would use the 3/4" all the way. Putting 1/2" to those fixtures MAY help with flow slowing down at other locations, but it would be worse for any flow changes in that bathroom.

 

[sundevil77]

Helpful. Given the vent is 12-14" away from proposed wall, am I ok to 90 degree

 

[MicEd69]

Yes, you can 90 to the left in your plan view and add the vent within 3 1/2 feet of pipe length from the P-trap weir. But I would add it as soon as you turn the corner. And a better layout would be to 45 over towards the vent stack for a better flow path.

 

[sundevil77]

Got it, thanks. What should distance be between branch vent and drain pipe?