Drain/Vent Scheme Input

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atnash

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Hi All. Going to DIY renovate a garage and laundry room and this will be my first major plumbing undertaking. I'm in California (2021 UPC based code). I'm looking for feedback on this proposed drain and vent scheme. There is a true rats nest of stuff going on in this area (gas dryer combustion air and exhaust, gas water heater air and exhaust, supply water lines for water heater and fixtures in this immediate region). I've accounted for all of this in the scheme, which is the source of a lot of the seeming excessive complexity.

Beyond comments on the scheme, I've got a few other related questions:

  • Any issues with joining all of the vents into one before going through the roof? Looking to minimize roof penetrations. I'd try to go through the wall, but that's not feasible here. Any need to add cleanouts to the vent branches (access would be available in the attic)?
  • Cleanout on the left will be behind a washer/dryer (can be moved if needed). Does that meet code requirements?
  • Can I take the tankless gas water heater condensate and air gap it to an exposed trap on the wall, then have that feed into the 3" stack? There's no ground around here to dump it on and I don't want to have it eat up concrete floors.
  • Can I have the tankless gas water heater PRV discharge into a metal garage sink via copper pipe? It would then drain through the sink trap shown on the right of the image. Not sure if the sink will buffer the temp down enough or if that will melt the drain pipe. Can discharge to garage floor, but not preferred if possible.
  • Permits have already been pulled for this scope. Would you think this portion of DWV piping should be isolated and pressure tested for inspection (then connected to existing drain after passing pressure test)?
r/Plumbing - Drain/Vent Scheme Input
 

wwhitney

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0) If I'm correctly understanding your rendering, that up/down the page is vertical and it's more or less isometric, so the sink and the washer are on a lower floor, and the WC is on an upper floor [although that seems weird], then the basic connectivity and venting is OK. But what type of sink is it? If it's a lav, then the drain after the vent takeoff can be 1-1/2" as shown, but if it is a laundry sink or utility sink, the drain needs to be 2" after the vent takeoff. So the vent takeoff would need to be via a 2x1-1/2x1-1/2 upright combo (meaning barrel at 2% slope, branch inlet pointing up).

Also, there is a fitting called a "double elbow" but I think you just mean two elbows, one after another. In which case the upstream elbow (going from horizontal drainage to vertical drainage) can be a quarter bend, but the lower elbow (vertical to horizontal) needs to be a LT90.

1) No issues

2) The UPC rule on cleanout access is 707.8, which you can see here: https://up.codes/viewer/california/ca-plumbing-code-2022/chapter/7/sanitary-drainage#707.8 The answer to your question depends on the interpretation of "readily accessible," which the UPC defines as "Having a direct access without the necessity of removing a panel, door, or similar obstruction." So if a washer/dryer is a "similar obstruction," that would not comply. Or if it is a dissimilar obstruction, it would be OK. Definitely a judgement call, although I lean towards it being a similar obstruction.

3) I think yes but I haven't found the appropriate section of the UPC/UMC that would specify whether you need to neutralize the condensate. The trap would need a vent and I would expect that you'd need an air gap. This answer is incomplete.

4) Yes, you can discharge into the sink. See UPC 608.5 https://up.codes/viewer/california/...chapter/6/water-supply-and-distribution#608.5 "Discharge pipe shall discharge independently by gravity through an air gap into the drainage system or . . ."

5) No opinion, I think you'd need to ask the agency that issued the permit. The typical way you'd do such a test is to install a test tee at the junction between the new piping and the existing piping (looks like there is only one such junction). Then you can use an inflatable test plug installed in the tee to block the 3" stack and test everything upstream of the test tee.

Cheers, Wayne
 

atnash

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0) If I'm correctly understanding your rendering, that up/down the page is vertical and it's more or less isometric, so the sink and the washer are on a lower floor, and the WC is on an upper floor [although that seems weird], then the basic connectivity and venting is OK. But what type of sink is it? If it's a lav, then the drain after the vent takeoff can be 1-1/2" as shown, but if it is a laundry sink or utility sink, the drain needs to be 2" after the vent takeoff. So the vent takeoff would need to be via a 2x1-1/2x1-1/2 upright combo (meaning barrel at 2% slope, branch inlet pointing up).

Also, there is a fitting called a "double elbow" but I think you just mean two elbows, one after another. In which case the upstream elbow (going from horizontal drainage to vertical drainage) can be a quarter bend, but the lower elbow (vertical to horizontal) needs to be a LT90.

1) No issues

2) The UPC rule on cleanout access is 707.8, which you can see here: https://up.codes/viewer/california/ca-plumbing-code-2022/chapter/7/sanitary-drainage#707.8 The answer to your question depends on the interpretation of "readily accessible," which the UPC defines as "Having a direct access without the necessity of removing a panel, door, or similar obstruction." So if a washer/dryer is a "similar obstruction," that would not comply. Or if it is a dissimilar obstruction, it would be OK. Definitely a judgement call, although I lean towards it being a similar obstruction.

3) I think yes but I haven't found the appropriate section of the UPC/UMC that would specify whether you need to neutralize the condensate. The trap would need a vent and I would expect that you'd need an air gap. This answer is incomplete.

4) Yes, you can discharge into the sink. See UPC 608.5 https://up.codes/viewer/california/...chapter/6/water-supply-and-distribution#608.5 "Discharge pipe shall discharge independently by gravity through an air gap into the drainage system or . . ."

5) No opinion, I think you'd need to ask the agency that issued the permit. The typical way you'd do such a test is to install a test tee at the junction between the new piping and the existing piping (looks like there is only one such junction). Then you can use an inflatable test plug installed in the tee to block the 3" stack and test everything upstream of the test tee.

Cheers, Wayne
Thanks Wayne, I greatly appreciate your input. All of your interpretations/assumptions are correct.

Yes, the intent is that it's a laundry/utility sink. Do you think it would be prudent to just run it as 2" all the way to the sink? I haven't selected the sink yet.

Point taken regarding accessibility of the cleanout. I'll hunt around for a better spot for it.

For the condensate, I went and reread. 814.1 is saying that piping shall be corrosion resistant (I think ABS would qualify?) and that it needs to go through an "indirect waste pipe". Rinnai's documentation also specifies an air gap for the condensate. Would I meet all of those requirements if I wye into the sink tailpiece? Providing the necessary vent for my initial plan seems almost infeasible given the mess of stuff going on here. Also, I couldn't find anything about neutralizing in the code and Rinnai's documentation says its optional. I'm also seeing in 814.3.1 that the condensate line will need its own cleanout.

Thanks for bringing up the test tee. I demo'ed one of those (not understanding what it was) from that exact location, so I'll just put it back.

Again, thanks much for your detailed input.
 

atnash

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Thanks much for catching that. For my further understanding: 1 1/2" vent gives 8 DFU, which I'm under (3 WC + 2 shower + 2 laundry sink = 7 DFU), but the 8 DFU value in Table 703.2 has footnote 3 stating "Except for six-unit traps or water closets". Does that footnote mean no 3" traps or water closets allowed on 1 1/2" vent? Not trying to argue, just trying to understand where you're coming from to avoid more rookie questions.
 
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wwhitney

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Does that footnote mean no 3" traps or water closets allowed on 1 1/2" vent?
Precisely. A quirk of the UPC.

Do you think it would be prudent to just run it as 2" all the way to the sink?
I've never seen a sink with a 2" trap, but my experience isn't that broad. I'd just go with a 1-1/2" trap to a 2x1-1/2x1-1/2 san-tee.

Cheers, Wayne
 
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