Drain Arrangement

[GLG]

The photo shows what will be a basement bathroom sink tie-in. The 1.5" horizontal pipe will go to the trap of the sink about 5' away. The 2" vertical pipe goes to vent and as shown ties into a 4" waste stack.
Will this arrangement meet code? If not, why not.
Thank you. GLG

 

[wwhitney]

For the IPC, in force in MD, if you use a 1-1/4" sink trap, then the trap arm (all the pipe from the trap to that san-tee in the picture) is limited to 5' of run and 1-1/4" of fall. But if you use a 1-1/2" trap, then it's 6' of run and 1-1/2" of fall.

As long as you comply with those limits, if the 2" line on top of the san-tee is a dry vent that goes through the roof, with nothing draining into it, that DWV arrangement complies with IPC. Of course, you've just shown a small picture, so I can't comment on any of the other bathroom fixtures, etc.

Cheers, Wayne

 

[Sponsor]

 

[Reach4]

I suspect that vertical pipe feeding the santee is not a dry vent. That is, I suspect it includes drainage from a floor above.

If that is the case, you should vent the new lavatory, and under IPC 2018, that could be done with an AAV (air admittance valve).

Are you adding a toilet or shower too?

 

[GLG]

The 2” vent is a dry vent.

So the 2”x4” wye fitting is acceptable in this application?

 

[Terry]

The 2” vent is a dry vent.

So the 2”x4” wye fitting is acceptable in this application?

A dry vent is good.,

 

[Reach4]

The 2” vent is a dry vent.

So the 2”x4” wye fitting is acceptable in this application?

Yes.
The reason I had suspected that might not be a dry vent is because that wye was yellowed some. But if that santee was also in place already, then I think that would have been there to support a sink or standpipe for future use.

 

[GLG]

I suspect that vertical pipe feeding the santee is not a dry vent. That is, I suspect it includes drainage from a floor above.

If that is the case, you should vent the new lavatory, and under IPC 2018, that could be done with an AAV (air admittance valve).

Are you adding a toilet or shower too?

Yes there will be a toilet. The 4” waste stack, which serves a bathroom on the 2nd floor, goes into the slab and runs diagonally to the front wall of the basement where it exits the house to sewer. The concrete will have to be tore up to access that 4” line. This could be done, correct?

 

[wwhitney]

Yes there will be a toilet. The 4” waste stack, which serves a bathroom on the 2nd floor, goes into the slab and runs diagonally to the front wall of the basement where it exits the house to sewer. The concrete will have to be tore up to access that 4” line. This could be done, correct?

Sure. But that WC will need to be vented. And one way to do that is to use the lav drain and vent to wet vent the WC. Which will require that the lav drain join the WC drain before either one joins any other drains. So you wouldn't use that 4x4x2 wye for the lav drain if you are going to wet vent your WC.

Cheers, Wayne

 

[Reach4]

Correct. However if you can route the drainage from the vented lavatory to the toilet line, it could serve as wet vent for the toilet. So that would mean that you would not have to provide a separate dry vent for the toilet line. Once the lavatory drainage has been joined with drainage for another floor or a non-bathroom thing, then that cannot be used to wet vent a toilet or shower.

Dry venting a toilet can be hard because a dry vent needs to be vertical (within 45 degrees of plumb). A wet vent will not have that restriction.

 

[GLG]

Hate to ask this but could one of you sketch up what you mean.

I took a picture of the existing WC rough-in and 2" dry vent. If I put the bathroom at this location, could I connect a sink drain to that sanitary tee in the vertical pipe? Now it becomes a wet vent from the sanitary tee to WC drain in the concrete slab, correct? Is that per code then? This rough-in is located along the back wall of the house and I don't like its location.

Thank you.

 

[GLG]

Hate to ask this but could one of you sketch up what you mean.

I took a picture of the existing WC rough-in and 2" dry vent. If I put the bathroom at this location, could I connect a sink drain to that sanitary tee in the vertical pipe? Now it becomes a wet vent from the sanitary tee to WC drain in the concrete slab, correct? Is that per code then? This rough-in is located along the back wall of the house and I don't like its location.

Thank you.

 

[wwhitney]

So I marked up your last photo. Green = 1-1/2", Blue = 2", Red = 3", and Orange = 4". The little jogs at the wall/slab intersection on the blue and orange lines are supposed to be LT90s.

The green is a lav tailpiece, trap and trap arm, ending at the san-tee you have. The blue is then the lav vent and lav drain. Everything under the slab is a hypothetical but shows the correct connectivity for wet venting the WC.

So if you ignore the orange, that's likely similar to what you have under the slab there (no idea where the combined WC/lav drain ends up going). I put in the orange to represent the 4" stack in your first photo. And then the drawing shows how the lav and WC should be connected with respect to the 4" line. (And I ran out of room for the final 3"/4" wye outlet at the bottom, it is implied).

The use of wyes (or combos) for 3-way horizontal drain connections (2 inlets, 1 outlet) is required, but the particular choice of which drain comes into straight inlet vs the side inlet is not important.

Cheers, Wayne

 

[GLG]

So I marked up your last photo. Green = 1-1/2", Blue = 2", Red = 3", and Orange = 4". The little jogs at the wall/slab intersection on the blue and orange lines are supposed to be LT90s.

The green is a lav tailpiece, trap and trap arm, ending at the san-tee you have. The blue is then the lav vent and lav drain. Everything under the slab is a hypothetical but shows the correct connectivity for wet venting the WC.

So if you ignore the orange, that's likely similar to what you have under the slab there (no idea where the combined WC/lav drain ends up going). I put in the orange to represent the 4" stack in your first photo. And then the drawing shows how the lav and WC should be connected with respect to the 4" line. (And I ran out of room for the final 3"/4" wye outlet at the bottom, it is implied).

The use of wyes (or combos) for 3-way horizontal drain connections (2 inlets, 1 outlet) is required, but the particular choice of which drain comes into straight inlet vs the side inlet is not important.

Cheers, Wayne

View attachment 84884

Thank you Wayne for that sketch. I totally understand that but unfortunately I will not be locating the powder room at that location. On my original picture, how will I need to modify that dry vent in regard to new WC and sink drain. The 4" waste stack enters the concrete and then runs diagonally to the front wall of the basement. The new WC drain will tie into that diagonal section of the 4" waste drain. Do I have to run the 2" vent into the concrete to provide a vent to the new WC? I would then have to plug the 2" wye which connects to the 4" waste stack, correct? The 1.5" connection as shown in the original picture to future sink would remain as is. Thanks again.

 

[wwhitney]

The orange line in my drawing represents the 4" line in your picture in the OP, so just take my drawing and line up the orange vertical with your 4" vertical. The 4x4x2 wye gets capped or removed. The 2" fittings are so close together you'd likely replace the 2" san-tee with a new one, possibly a bit to left to clear the capped 4x4x2 wye, and then jog the vent over with (2) 45s to reconnect.

The direction of pipes in the slab may not be accurate in my drawing, but the connection order is what matters: the 2" lav drain goes into the slab, hits the 3" WC drain, and only then the combined lav/WC drain hits the 4" horizontal line. Which is why the 4x4x2 wye side branch gets capped.

Cheers, Wayne

 

[GLG]

The orange line in my drawing represents the 4" line in your picture in the OP, so just take my drawing and line up the orange vertical with your 4" vertical. The 4x4x2 wye gets capped or removed. The 2" fittings are so close together you'd likely replace the 2" san-tee with a new one, possibly a bit to left to clear the capped 4x4x2 wye, and then jog the vent over with (2) 45s to reconnect.

The direction of pipes in the slab may not be accurate in my drawing, but the connection order is what matters: the 2" lav drain goes into the slab, hits the 3" WC drain, and only then the combined lav/WC drain hits the 4" horizontal line. Which is why the 4x4x2 wye side branch gets capped.

Cheers, Wayne

I understand now. Sorry for not picking that up. Thank you so much for your help on this. Regards, GLG