I'm in the process of remodeling a bathroom and need help with venting all of the fixtures (toilet/shower/lav). I was thinking on wet venting the shower and toilet from the lav's vent see the sketch below. I was told that this is possible (up to "code") if a 4" drain pipe is used for the water closet. To complicate matter I also need to drain a kitchen sink at this location. The kitchen sink has it own vent neat it.

Hi NJLJM:

Need a little more information... I figure this is an existing underground job... yes/no? If so, how much of it exists (I understand the 4"stack goes upstairs)?

The 2"double wye tap... do you mean you have a 4"x2" double threaded wye cast iron fitting there already?

As presented, I would have you wet vent the toilet by installing 2" waste and 2" VENT to SHOWER drain line. That vent would need to run full size 2" to vent of equal size or larger upstairs or in attic or penetrate roof separately. I would have you reduce lavatory vent to 1.5" and connect that into the 2" shower vent (in joist bay or upstairs in attic).

There is no 2.5" pvc or abs piping, so run 2" to pick up lavatory and kitchen sink. In fact, run 2" pipe underground for the kitchen sink as well. NO 1.5" waste pipes allowed underground.

All 90 degree turns on waste line need to be long sweep fittings (sold as long sweeps or can make these joining a 45 and a street 45 together). Long sweep 90s also needed as come out of the ground from horizontal to vertical at both sinks. Then I install a 2" dandy cleanout (see pic.) where you can access from under the sinks after they get installed.

Answer my questions... let me know your thoughts... Mark

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Mark, thanks for getting back to me. Congratulations on your promotion!

This is all happening in the crawl space (wood framing). The tub, toilet and lav were on the one story addtition but I moved and replaced the tub for a shower( now located on the 3 story sect. of the house). As you can imagen it is easier to vent the shower on the one story side than the three.

The 2" PVC vent at the Lav. will connect to a 3" (existing) cast iron pipe through the roof (one story).

I will be using a 4" wye with two 2" taps.

Thanks again

Ljm

Hi again ljm:

Sorry... but that shower needs a vent. And the kitchen sink connection prevents you from using the lavatory vent as a wet vent for the toilet or shower

So, in my opinion, best solution appears to be to wet vent the toilet using the 2" SHOWER VENT. And reduce the lavatory sink vent to 1.5"

Let me know what you think... Mark

Thanks, I had a feeling the kitchen drain was going to be a problem. Let me know if this works.

Ljm

What is that big circle with 4" pointing to it... and where is the kitchen sink drain now..

That's the cross section of the horizontal toilet drain. The kitchen sink connect at same location between the toilet and the bathroom sink.

LJM

Hey LJM:

I think you got it. The pic. Does not show the 1.5" vent at bath sink (shows circle and line, but pipe size got cut off), or even the kitchen sink...but I think I understand that kitchen drain pipe is same as 1st pic. you presented.

Fittings are so specific in plumbing...that area at "cross section of horizontal toilet drain"... lost me. But I am very LITERAL when it comes to pipes/vents.

Seems to me you understand that you needed to add the 2" vent at the shower to vent shower and toilet... looks good from there.

Let me know if need more... glad to help if I can... Mark

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