Is this a good way to handle a floor drain?

[DavidTu]

I have a 2" floor drain going into a 2" p-trap and then on into a 4" main drain in the basement floor. In order to keep the trap wet over time, I did a wye off the floor drain vertical and dropped a lav sink into it. The lav will of course have its own P-trap and vent in the wall as normal. What bugs me is that the lav is joining the floor drain ahead of the floor drain vent, which is of course after the P-trap. I don't see any other way to handle this but it does seem wrong to join drains before a vent. On the other hand it doesn't seem problematic in that the lav is going through the P-trap for the floor drain so it's not possibly going to siphon that off, which I believe is the primary concern of joining drains before venting. What is the right answer here?

 

[DavidTu]

tap...tap...tap.... hello? is this thing on?

 

[Sponsor]

 

[Reach4]

What was the question again?

A sketch of what you propose would probably be useful.

 

[Terry]

What was the question again?

A sketch of what you propose would probably be useful.

Yes, a sketch would be nice. I'm trying to wrap my brain around what your words are.

 

[Plumber69]

Why not use a trap primer and be done with it

 

[Plumber69]

I think he is doing this

 

[Cwhyu2]

That might be considered an indirect waste from the lav. plumber69

 

[DavidTu]

I think he is doing this

Yes this is correct, thanks for the sketch!

Kosher? If not why not? What's downside?

 

[Plumber69]

It will probably work. I don't know why you just wouldn't trap prime it. Ive tied in a sauna drain to a shower ptrap

 

[Cwhyu2]

Indirect waste, it does not affect the vent for the floor drain as the waste from the lav discharges to the inlet of the P-trap for the floor drain.
Not how I would do it but should be okay.

 

[Reach4]

If you do the indirect waste thing, there should not be a p-trap on the sink, and there should not be a vent pipe for the sink. I am not a plumber.

 

[hj]

The sink CAN have a "P" trap, but not a vent.

 

[DavidTu]

It will probably work. I don't know why you just wouldn't trap prime it. Ive tied in a sauna drain to a shower ptrap

I don't like the idea of a mechanical solution, would rather have it come from a regularly used sink.

 

[DavidTu]

The sink CAN have a "P" trap, but not a vent.

Why can't the lav be vented? What is the principle behind that?

As for indirect drain, this is not one since there is no air-gap.

As planned/proposed, the lav would have a p-trap and be vented as normal. Downstream its drain is simply wye-d with the floor drain, both of which go through a p-trap and are vented. The lav, then, would have its own p-trap/vent and also go thru the floor drain's p-trap/vent, but not via air-gap. What principles does this design violate?

Thanks.

 

[Reach4]

Why can't the lav be vented? What is the principle behind that?

Sewer gas from the vent can come out of the floor drain.

 

[DavidTu]

Sewer gas from the vent can come out of the floor drain.

I see. So an AAV at lav would solve this issue?

 

[Reach4]

I see. So an AAV at lav would solve this issue?

It would, I would think.

 

[DavidTu]

The sink CAN have a "P" trap, but not a vent.

Just want to double check with you--an AAV on the sink would be ok?