Bathroom plumbing - venting new bath

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mikemikemike13

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Hi,

This forum has been extremely helpful to me over the past few years. This is my first time posting as I'm feeling that I'm a bit in over my head on this bathroom remodel. I was hoping to get some input on my plumbing plans.

I'm adding a freestanding tub next to the existing shower drain and moving a double vanity about 12' from the 4" main stack. My main question is whether the bath can share a vent with the shower. The shower is on a 2" drain and has a 2" vent that connects to the main stack. It's my understanding that they can share the 2" drain, but I'm not sure if I have to vent the bath drain before connecting to the shared 2" drain.

My other question is whether I can connect the new 2" lav drain into the toilet drain using a 4x4x2 hub. I don't think there is an issue there. I will likely vent the lav with an AAV depending on how hard it is to make it into the attic.

I'm attaching a picture of the proposed plumbing and a picture of the layout of the bathroom for reference. The lines in red on the plumbing photo are what I'm adding. The rest is original. Any input on my plans would be helpful.

Thanks in advance!

-Mike

IMG-2252.jpgIMG-2253.jpg
 

wwhitney

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2" bath drain could join the shower downstream of its vent, and be wet vented by the shower, if the resulting tub trap arm is not too long. Otherwise, it needs a dry vent sufficiently close to the trap.

Lav drain can join the WC drain and wet vent the WC, some would prefer to see the joint via a horizontal wye instead of an upright combo. You can't use a quarter bend with heel inlet for the WC/lav joint, that is the same pattern as a san-tee, and a san-tee can't be used on its back for drainage.

Cheers, Wayne
 

mikemikemike13

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2" bath drain could join the shower downstream of its vent, and be wet vented by the shower, if the resulting tub trap arm is not too long. Otherwise, it needs a dry vent sufficiently close to the trap.

Lav drain can join the WC drain and wet vent the WC, some would prefer to see the joint via a horizontal wye instead of an upright combo. You can't use a quarter bend with heel inlet for the WC/lav joint, that is the same pattern as a san-tee, and a san-tee can't be used on its back for drainage.

Cheers, Wayne
Thanks so much for the info. I plan to use 2" for the bath drain so the trap arm won't be too long. I was definitely thinking of using a quarter bend with heel inlet, so thanks for calling that out. Joining with a horizontal wye would actually be easier for me anyway since the lav drain will be closer to the wall and I'm going to have make the change from copper to pvc anyway before the toilet.
 

mikemikemike13

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@wwhitney thanks for your input. After opening up the floor some things have changed. I was hoping to get your input on my new plan. I don’t have room to fit a wye before the toilet so my new 2” lav drain would connect to the 3” toilet drain via an upright combo.

Could I drain the bath into the new 2” lav drain instead of the shower? It would save me drilling through quite a few joists. If so, would I need to vent it before or could it use the lav vent?
 

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wwhitney

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You'll need to check the code language in the NSPC on horizontal wet vents, but I generally think the upright combo is fine for the WC to wet vent connection. There is a school of thought that it needs to be a horizontal wye, but I don't see the physics or code language support (in the IPC or UPC) for that. Although I recall the IRC does say it has to be horizontal. A middle ground is a wye rolled up 45 degrees plus a 60 degree bend.

Certainly you can drain the bath into the lav drain. If the tub trap arm, from trap to horizontal wye where the it joins the lav, meets all the NSPC trap arm requirements (not sure on the length limit, but definitely at most one pipe diameter fall, the trap weir rule), that's fine. Here the wye must be horizontal, because of the trap weir rule. WCs are the exception that don't have to meet the trap weir rule.

Cheers, Wayne
 

mikemikemike13

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So, I ended up cutting everything out at the old copper fitting and used a shielded coupling to connect to 3” pvc. I was able to fit a double wye behind the WC this way. I’m going to put the subfloor in next weekend and I’m going to be running pex and checking for leaks this week. Just wanted to post some pictures to see if anything looks wrong before I close it up.

BTW, there will be a studor vent under the vanity for the lav and bath drains and the shower will be vented via that santee. The old copper lav drain and supply lines will be removed.
 

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wwhitney

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So, when using a double wye on the horizontal like that, it's important to get the two side entries at exactly the same pitch; if one entry is sloped higher, the other entry ends up sloped lower. It's also best practice or required to slope the barrel (straight path) at 3%, as the with the side entries even, they will be sloped at 71% of the barrel slope.

The venting looks fine to me, assuming the NSPC doesn't have some unfamiliar requirements.

Cheers, Wayne
 

mikemikemike13

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So, when using a double wye on the horizontal like that, it's important to get the two side entries at exactly the same pitch; if one entry is sloped higher, the other entry ends up sloped lower. It's also best practice or required to slope the barrel (straight path) at 3%, as the with the side entries even, they will be sloped at 71% of the barrel slope.

The venting looks fine to me, assuming the NSPC doesn't have some unfamiliar requirements.

Cheers, Wayne
Just checked and it is not exact. I have a 3% (3/8"?) slope on the barrel but the lav side wye is slightly lower than the shower side inlet which results in a 1/8" slope on the lav side for the last foot into the main stack. The rest of the line is just under 3/8" slope. I have 1/4" slope on the shower side wye.

Not having the right tools led me to drilling the holes just big enough for the pipe without much play so the only way to fix it would be to cut it out and start over.

Is this a huge deal?

Also, as you can see from the pictures I have 3x2" reducers at the wyes. Not sure if that affects the slope.
 

wwhitney

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Not sure.

Obviously all of the 2" piping is supposed to have a minimum 1/4" per foot fall. Sounds like you have a one foot section (just upstream of the double wye) where the fall across that foot is only 1/8".

Certainly a technical violation, but is it likely to actually cause trouble? I.e. because a place for a clog to happen in the future? I don't have the experience to know.

Cheers, Wayne
 

Jeff H Young

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your good nice job ! I'm not crazy about the double wyes but they should be fine . not a lot of good ways to do that and you got it done a pretty good way
 

mikemikemike13

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Thank you, all! I ran water through all the pipes and no leaks and everything seems to drain well and p-traps are holding water. I was worried about the Fernco fitting but no leaks. I've noticed that it has essentially been "in use" since I installed it since it is connected to one side of double santee on the main stack and there is some crossover when the other bathroom is used. From what I've read on here, this is not ideal but how they used to do it in the old days and I don't have access to fix all of that.

I finished the PEX this past weekend and ready to put the subfloor in this weekend. Anything I should double/triple check before installing the floor?

One other question I had: do you all actually tighten the Fernco to 60/lbs torque? Or just tighten by hand, or impact driver? I have a torque wrench, I would just need to buy an adapter to use the 1/4" socket, not sure if necessary though.

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wwhitney

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Hex nut on Fernco is 5/16" I believe. Use a purpose-built torque wrench or your general purpose torque wrench, if 60 in-lbs / 5 ft-lbs is within its range.

Cheers, Wayne
 

Jeff H Young

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A plumber has a 5/16 torque wrench pre set at 60 inch pounds its a T handle and very convenient we also have 3/8 wrench that's 80in. Haven't bought one in many years kinda pricey for a few joints . I've got a bit of a feel using a regular 1/4 inch ratchet or a nut driver . Its a good idea to check torque again a day later they kind of settle. plus we are supposed to test don't want to cover till you are sure its leak free

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