1.5" vanity drain into a 3" toilet pipe quick question on if OK and clean out.

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ARC

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Hi and thanks again. Can I drain my 1.5" (could be 2" if needed) into the back of my 3" toilet drain? I don't see why not but maybe it's not best practice. Between some conduit and the joists I don't believe I have enough headroom to run the 3" pipe all the way back to the vertical sink pipe and get enough slope.

Mainly I want to add a cleanout somewhere since my 100-year-old CI doesn't have one. Can it be on the back of the 1.5" pipe (drawing # 1) or does it need to be part of the 3" size (drawing #2)? I think I read in the UPC code that it says it needs to be the same diameter as the main pipe so 3"? If so should I use a Tee of a Wye?

If this is a bad idea I was originally going to plumb it like in drawing number 3, but the sink drain now happens to be very much so in line with the toilet. Which way would you do?

Thanks again.
 

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wwhitney

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Your 3" san-tee with 2" side inlet, is the pipe above it a vent only, or does it received drainage from a fixture? If the latter, is it a fixture on the same floor, or a floor above?

The double san-tee itself, is it cast iron or plastic? Does the 2" inlet have some radius to it, like the 3" san-tee inlet does? And how is your 2" shower line vented, is it via that san-tee? Which would be fine if it the trap is within 5' of the san-tee, with the trap arm having the proper slope.

The answers to those questions will have some bearing on which of #2 and #3 are allowable. I imagine a 3" cleanout is preferable to a 1.5" cleanout. The joist bay with 3" closet bend, does it have room for a flat 3x3x2" wye, along with a 2" street 45 to bring the 2" side inlet parallel to the 3" inlet on the wye?

Cheers, Wayne
 

ARC

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@wwhitney Thanks for the reply. Sorry, guess I should have added more details. I added a couple more drawings to hopefully clarify and might be better than me explaining.

The Cast Iron 3" san-tee with the 2" side inlet comes off the shower. I will vent it near the shower P-Trap. Drawing #3 (original plan) would be to connect the vanity after the shower vent. The Vanity has a separate roof vent just after it's P-Trap.

The whole stack is hub cast iron and in good shape, but the side inlet hub only has room for a 2" pipe. Everything is just from the 1st floor and no connections from the second.

The toilet is on a 90˚ long sweet combo just a couple of inches below the joists. The joists run perpendicular to the toilet combo and vanity pipe. Hence that is why I can't just do a 3" all the way to the vanity since I cross joists/conduit before I get enough slope to be code.
 

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wwhitney

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Just looking at your last two drawings, in the first one, the lavatory dry vent would be wet venting the toilet. [Because under the UPC, a fixture drain can't join another drain before it is vented, so the only way to join the drain is if you are wet venting the toilet.] So everything upstream from the 3" would need to be 2", not 1.5" (except the lav trap arm). And the rest of the stack above the san-tee would be redundant, no venting takeoff is required there. Some would say that the toilet would have to join the lavatory drain via a horizontal wye, rather than coming in from above, but I don't see any language supporting that in the UPC. It may be a better practice, however, I don't know.

In the second drawing, everything is individually vented. Before the UPC adopted wet venting (sometime in that last decade or two, if I recall), it would have been the only option.

BTW, is the shower really a 1.5" trap? The UPC requires a 2" trap, and you show a 2" drain line. Also, I'm not familiar with any amendments Minnesota may have made to the UPC.

Cheers, Wayne
 

Jeff H Young

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tried to follow this . why do this assuming you have a lav already? you just want a clean out in the 100 year old system is what Im seeing nothing about a remodel or repipe?
 

ARC

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@wwhitney Once again thanks a bunch. I really appreciate the knowledge. So do you think I should do the 2" Lav to 3" toilet or picture 2? Sounds like I can according to you and I have room for the slope of a 2". Would I still add a 3" cleanout with either a wye on its back or a tee on its back? One other question, please. Are you saying the san-tee of the "lav" is redundant since it's wet vented with the 2"?

The lav pipe just happens to be really lined up so the toilet combo would have to come in from up top if at all. It's nearly too close to the stack as is. And yes the shower trap is 2" but I appreciate you double-checking as I forgot that it had to be. The vertical pipe into the trap is 1.5" adapted to 2" at trap since 1.5" pipe setup is what came for the shower with the drain.

@Jeff H Young Yes this is a remodel. Clawfoot into an alcove tub/shower. My girlfriend moved in with her daughter a bit back and I want them to have a nice bathroom. All fixtures/plumbing was on the toilet side but moved the lav over. My toilet wasn't even 14" on center and my lav was vented less than 6" above the rim line so in a way I'm getting more in code. I'm handy but plumbing is a new venture for me and I like learning all the rules.
 

wwhitney

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@wwhitney Once again thanks a bunch. I really appreciate the knowledge. So do you think I should do the 2" Lav to 3" toilet or picture 2? Sounds like I can according to you and I have room for the slope of a 2". Would I still add a 3" cleanout with either a wye on its back or a tee on its back? One other question, please. Are you saying the san-tee of the "lav" is redundant since it's wet vented with the 2"?
1) No opinion
2) Not a tee on its back, you could use a wye rolled at least 45 degrees above horizontal, if that would provide access for rodding.
3) No, not the the lav san-tee. In option 1, the lav dry vent obviously vents the lev, and it wet vents WC. And the shower is individually vented. So if the stack itself is not venting anything else (seems like single story?), then the vent above that double 3"/2" san-tee is no longer needed (other than possibly for the rule that the aggregate vent through the roof must be at least 3" (or 4" if there are 4 or more WCs)). But since it's cast iron and existing, might as well leave it.

Cheers, Wayne
 
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Jeff H Young

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btw ARC a tub or tub shower only requires an 1/1/2 trap and a shower requires a 2 inch trap.
nothing wrong with 2 inch though
 
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ARC

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@Jeff H Young. Thanks for the clarification. Out of curiosity, is that because there is an overflow and it technically gets air from there too?

@wwhitney. I get the Lav to WC wet vent idea better this morning after some coffee. So you're saying even the vent coming out of the Lav needs to be a 2" since it's wet venting a WC, right? Makes sense. I'd have to do the original plan into the 2" pipe then since I'm venting the Lav with 1.25" because it needs to run through some doubled 2x6 joists. Thanks for saving me from making a code mistake.

This conversation was super helpful for me and I hope it helps others in the future.
 

wwhitney

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Out of curiosity, is that because there is an overflow and it technically gets air from there too?
I assume the allowance for a 1-1/2" drain for bathtub is because there's a large basin to hold any backup. Unlike a shower where a significant backup could overflow the curb.

So you're saying even the vent coming out of the Lav needs to be a 2" since it's wet venting a WC, right?
Yes, although I'd remove the word "wet." Any WC vent under the UPC has to be at least 2". As a separate requirement, any wet vent under the UPC has to be 2".

So if you were wet venting just a shower, say, then the lav drain/wet vent would still have to be 2", but the dry vent would only have to be 1.5".

Cheers, Wayne
 
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Jeff H Young

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ARC, As for why the difference in trap arms . could be a number of reasons perhaps one being a bath tub wont overflow as easy as a shower. I hear members of an organization petition for a code and some vote takes place. so I'm thinking it boils down to why does one guy vote one way and someone else votes another ? So many major difference between one code and another don't know why that is either.
 
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