Adding Utility Sink next to Bathroom

[Martin Jahn]

I am working on adding a single basin utility sink in the garage, adjacent to an existing bathroom. The existing bathroom has a sink with a 2" drain line going to to the slab and a 1-1/2" vent line. The distance between the existing 2" vertical drain line and the outlet of the new utility sink is going to be just over 36". The top of the bathroom sink will be about 4" higher than the top of the utility sink.

Based on what I have read, I need to install a second sanitary tee below the existing one that the bathroom sink is using to feed over to the utility sink (due to the large structural post, the horizontal feed to the Utility Sink with run outside the wall but inside the bathroom sink cabinet).

Then also run a new vent line up from the sanitary tee at the utility sink and join the existing vent (in my case above the ceiling).

Does this sound/look correct?
Should I being using 2" for the drain line to the utility sink or can I use 1-1/2"?
Is there any dimensions I need to concerned about such as relative height between the two sanitary tees where each fixtures P Trap will connect?

Is there an easier way?

 

[wwhitney]

Something like what you propose may be possible, but first you need to determine how the other fixtures in your bathroom are vented. Because one likely possibility is that they are wet vented by the bathroom sink. And if that is the case, you can't add the drainage of a non-bathroom fixture where you show it. It would have to connect downstream of any wet vented fixture.

As to the drain size for the utility sink, it should be 2" starting at the new san-tee. Utility sink is not a category under the California Plumbing Code, but only bar sinks and lavatory are allowed to have a 1-1/2" drain.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#702.0

Cheers, Wayne

 

[Sponsor]

 

[Martin Jahn]

Something like what you propose may be possible, but first you need to determine how the other fixtures in your bathroom are vented. Because one likely possibility is that they are wet vented by the bathroom sink. And if that is the case, you can't add the drainage of a non-bathroom fixture where you show it. It would have to connect downstream of any wet vented fixture.

As to the drain size for the utility sink, it should be 2" starting at the new san-tee. Utility sink is not a category under the California Plumbing Code, but only bar sinks and lavatory are allowed to have a 1-1/2" drain.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#702.0

Cheers, Wayne

Hi Wayne,

The only other fixture in the bathroom is a toilet. Based on what I can see in the attic, the toilet has it's own 2" vent pipe. So the current 1-1/2" vent for the existing sink is NOT a wet vent, so then the proposed arrangement will be good.

Any other concerns or recommendations?

Thanks,

Martin

Something like what you propose may be possible, but first you need to determine how the other fixtures in your bathroom are vented. Because one likely possibility is that they are wet vented by the bathroom sink. And if that is the case, you can't add the drainage of a non-bathroom fixture where you show it. It would have to connect downstream of any wet vented fixture.

As to the drain size for the utility sink, it should be 2" starting at the new san-tee. Utility sink is not a category under the California Plumbing Code, but only bar sinks and lavatory are allowed to have a 1-1/2" drain.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#702.0

Cheers, Wayne

Something like what you propose may be possible, but first you need to determine how the other fixtures in your bathroom are vented. Because one likely possibility is that they are wet vented by the bathroom sink. And if that is the case, you can't add the drainage of a non-bathroom fixture where you show it. It would have to connect downstream of any wet vented fixture.

As to the drain size for the utility sink, it should be 2" starting at the new san-tee. Utility sink is not a category under the California Plumbing Code, but only bar sinks and lavatory are allowed to have a 1-1/2" drain.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/7/sanitary-drainage#702.0

Cheers, Wayne

 

[wwhitney]

Great, if the existing sink is not wet venting anything, then your plan is sound.

Your new san-tee should be 2x1-1/2x1-1/2; the outlet of the san-tee can hit a 2" LT90 and run over to your vertical 2" sink drain. There it can hit a san-tee or a combo, your choice. And your 1-1/2" vent can connect with the existing 1-1/2" vent anywhere that's at least 6" above both sinks, so obviously in the ceiling would be fine. No particular height requirements on the drainage side.

What's that hose coming in from the right in your picture?

Cheers, Wayne

 

[Martin Jahn]

Great, if the existing sink is not wet venting anything, then your plan is sound.

Your new san-tee should be 2x1-1/2x1-1/2; the outlet of the san-tee can hit a 2" LT90 and run over to your vertical 2" sink drain. There it can hit a san-tee or a combo, your choice. And your 1-1/2" vent can connect with the existing 1-1/2" vent anywhere that's at least 6" above both sinks, so obviously in the ceiling would be fine. No particular height requirements on the drainage side.

What's that hose coming in from the right in your picture?

Cheers, Wayne

Hi Wayne,

Thanks for confirmation, I'm off to buy my supplies now.

The hose is from water softener back flush line.

Appreciate your assistance.

Thanks,

Martin

 

[wwhitney]

Ah, I'm not so familiar with waster softeners. The sink tailpiece with branch inlet is a nice way to bring the drain into a trap. But I wonder if an air gap is required? The answer is probably in Chapter 8 of the UPC, which I haven't looked at much.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/8/indirect-wastes#8

Cheers, Wayne

 

[Jeff H Young]

drain needs to be 2 inch on the sink but wet venting from lav trap arms are 1 1/2 up to 42 inches length. dont know if that would be preferable to you.
cant have potable water connected directly like that to waste. good call wayne! maybe dump it over the utility sink in garage. might concider fire rating on the garage wall ill usuall put a cast iron sweep there