Need help with DWV

Old 10-20-21, 02:29 PM
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Need help with DWV

My plumber backed out on us and have not been able to get any call backs from any others, so looks like we are on our own. I am trying to plan my under slab stuff so we can pour.
The drain seems pretty straight forward, but the venting has me confused. See plumbing layout below. Note we will have two sinks in the master bath, plan shows one. Also we have a one room loft directly above both bathrooms, so hopefully can vent around that room?

1. What fixtures should/can I combine to vent together?
2. Do all vent pipes need to connect under slab close the all p-traps then come up a wall?

thanks for any advice and help

Old 10-21-21, 04:00 PM
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I'd lay it out something like this. Red indicates vents.

Other notes:
* Vents on exterior walls are difficult to deal with once you get to the roof. You may not have a choice for the kitchen, but the laundry should certainly go up an interior wall if possible
* 2" vents for each bathroom sinks. That covers the toilet and shower/tub. 3" vent is not required in the bath
Old 10-21-21, 05:29 PM
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Wow thanks for the diagram, it really helps to see it. So 3Ē is not required for toilet vents, just drain?
Should I combine the kitchen sink and washer vents in the attic and vent just those through the roof? Or can they attach to the bathroom vents also?
thanks for your help.
Old 10-22-21, 04:49 AM
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The answer to your questions is in the plumbing code. Since you are going to be doing the work I strongly suggest that you actually read it since there are numerous potential pitfalls if you are not prepared.

You can use different size vent pipes depending on your needs. Each pipe has the capacity to handle multiple fixtures. For example, a 2" vent pipe can handle up to 24 fixture units. Each bathroom sink counts as one, a tub or shower counts as two, and a modern toilet three. The code also specifies the maximum distance the vent connection can be from the trap it is protecting. The distance varies depending on the size of the pipe.

Venting is one area that many people screw-up so it will pay to be educated up front. Another area that catches many people is when to use "sanitary T's" versus "Wye's".

On a side note. You did not say where you are located but I try to avoid piping on exterior walls as much as possible because of the freezing risk it poses. And, as Zorfdt mentioned dealing with vent pipes in an exterior wall is a pain. If your vents are located in the interior of the home they can more easily be combined in the attic to minimize the pentrations through the roof.
Zorfdt voted this post useful.
Old 10-22-21, 05:58 AM
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Thanks Pilot, yes venting does seem to be where Iím most confused. Iím probably over thinking it which I tend to do. I have been reading through the IPC code and the Louisiana Plumbing Code. I am in extreme south Louisiana, so freezing isnít a major problem. Also my exterior walls are getting closed cell spray foam.
I think I was confusing the 3Ē toilet drain with vent size. Thanks for the help. Iím trying to learn before I do.

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