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.