Change shower to wet vent

[snafflekid]

I am remodelling a bath to include a larger shower stall and this will require Lavatory 1 and the shower vent to move to the other side of a joist. Also I am replacing this corroding galvanized plumbing leg with PVC back to the cast iron wye.

I am weighing some options on the plumbing change. Will it be okay to remove the dry vent from the shower drain leg and use the two lavatories to provide wet venting to the shower? I prefer to run the shower drain under the joist and use a horizontal combo wye. I prefer not to notch the joist. I could also use a shower drain configuration where the outlet is on the other side of the joist, but that's not my favorite choice either.

 

[wwhitney]

Yes, lav 1 can wet vent the shower as shown. California follows the UPC, which requires any wet vent to be 2", as you've drawn.

How much are you replacing? There's a couple issues in the existing: these days back to back WCs are not to be plumbed with a double san-tee; a double wye is preferred. And the shower can't be vertically wet vented below the WCs, it should be above the WCs (or it could join the other 2" branch and be wet vented horizontally).

Cheers, Wayne

 

[Sponsor]

 

[snafflekid]

the shower can't be vertically wet vented below the WCs, it should be above the WCs (or it could join the other 2" branch and be wet vented horizontally).
Cheers, Wayne

That is probably why the shower is vented the way it is currently. The venting seemed redundant to me. Hmm. It is not clear to me what you mean by joining the other branch and horizontally wet venting

 

[wwhitney]

Sorry, in my last post I meant the "tub/shower", not the shower you're asking about. The tub/shower is current wet vented vertically below the WCs, which is not allowed.

Cheers, Wayne

 

[snafflekid]

Ah I see, thanks. Actually the tub/shower leg rises up to the level of the closet bends where there is a sanitary tee and vertical vent. It is quite a work of art

 

[wwhitney]

Ah, the tub is separately vented, which is not shown on your diagram. That part is fine, then.

That fitting you've labeled double san-tee, I think it may be a different fitting, which may be allowed for back to back WC. A face on picture would clarify that. Although if you are planning to replace it anyway, a double wye is the way to go.

Cheers, Wayne

 

[snafflekid]

Now that I am looking closer I think you are right. I do not have a great picture but I think it is a double wye with built in 45 degree bends. Not quite how I expect a combo wye to look.

 

[Reach4]

but I think it is a double wye with built in 45 degree bends. Not quite how I expect a combo wye to look.

A regular "combo" is a wye + a 45.

 

[wwhitney]

I'm not super familiar with cast iron, but I think that's a Figure Five Double Fixture Fitting. So better than a double san-tee.

If you're not having any trouble with one WC's flush affecting the water level in the other WC, it would be fine to leave it in place. But if you do replace it, go with a double wye instead.

Cheers, Wayne

 

[snafflekid]

Is it correct that I cannot transition the shower drain from horizontal to horizontal because that would require a portion of the vertical wet venting to be below the closet bend level?

What if I directly connected a dry vent to the horizontal branch draining Lav 1, Shower and Lav 2? Somewhere near the cleanout or downstream of the shower p trap, either on the main leg or the shower leg?

And I am curious what is the problem with the vertical wet vent below the toilet?

 

[Reach4]

Is it correct that I cannot transition the shower drain from horizontal to horizontal because that would require a portion of the vertical wet venting to be below the closet bend level?

You might want to clarify that question. It is too complex for me at the moment.

 

[snafflekid]

That was confusing. I hope this is better. Is there a problem with running a dry vent directly to the Lav 1, shower, Lav 2 branch, considering the fact that this entire branch is below the level of the closet bends?

 

[wwhitney]

Is it correct that I cannot transition the shower drain from horizontal to horizontal because that would require a portion of the vertical wet venting to be below the closet bend level?

I don't quite follow the question, but I'm pretty sure the answer is no. Now that you've clarified the tub venting, the only wet venting in your "new" diagram is between the lav 1 san-tee and the combo where the shower drain joins the lav 1 drain. Anything that happens downstream, e.g. like what the WCs are doing or where they are located, has no impact on that wet venting.

And I am curious what is the problem with the vertical wet vent below the toilet?

Well, the UPC and IPC are both clear that on a vertical wet vent, the WC has to be the lowest wet vent, a fixture below can't be vertically wet vented. I assume the idea is that the volume and rapidity of the WC discharge could disrupt the vent for any fixture below.

Cheers, Wayne

 

[wwhitney]

That was confusing. I hope this is better. Is there a problem with running a dry vent directly to the Lav 1, shower, Lav 2 branch, considering the fact that this entire branch is below the level of the closet bends?

No, but it would be redundant. Because by the time Lav1, shower, and lav2 have all combined, each one has had to be properly vented already.

Cheers, Wayne

 

[Reach4]

That was confusing. I hope this is better. Is there a problem with running a dry vent directly to the Lav 1, shower, Lav 2 branch, considering the fact that this entire branch is below the level of the closet bends?

There is never a problem running dry vents to everything.

Having the closet bend higher is not a problem. You can then pipe down to join the wet vent last under UPC.

Must the toilet then enter the wet vent from the side? Surprisingly hot topic. https://terrylove.com/forums/index.php?threads/is-this-wet-vent-of-a-toilet-ok-theoretical.89201/

 

[snafflekid]

Checking to see if I understand how to extend the dry venting in the remodel.

 

[wwhitney]

No, two problems:

(1) If you want to dry vent the shower, it has to come off the trap arm, before the shower drain joins with anything else.
(2) The UPC (in force in California) does not allow a vent takeoff via a san-tee on its back. It has to be a combo.

But you don't need to dry vent the shower. Wet venting it via lav 1 is fine.

Cheers, Wayne

 

[wwhitney]

PS. If you really want to dry vent the shower, but the only wall for a vent is above the 2" horizontal line running beneath the 2 lavs, then if you have the height available, you could do this:

Raise the shower trap and/or lower the horizontal 2" drain so that your shower drain can be ~4" above (c-t-c) the horizontal drain when they overlap in plan. Bring the shower trap arm to the wall line and turn with a 45 to be directly above and parallel to the drain. Hit a combo for your dry vent takeoff. Then hit a vertical street 45 plus wye to join with the horizontal 2" drain.

But wet venting is simpler.

Cheers, Wayne

 

[snafflekid]

I want to do things as simply as possible

There was confusion in the beginning about the tub/shower arm vent, which I forgot to draw in the diagram. So the tub/shower looked like it was being wet vented through the 3"soil stack, which would be wrong.

And that confused me to think that you referred to the shower stall not being properly vented by the wet vent from Lav 1, which did not seem like a problem, so I was trying to figure out why.

Which led me to suggest to dry vent the whole Lav 1, shower, Lav 2 arm. LOL. Nope, no I prefer not. But I understand the problem much better now!

I need a beer, or wine, or both ...

 

[snafflekid]

I took a close up of the cast iron fitting that drains the water closets. The turn is more than 45 degrees, maybe 60?

Thank you very much, Wayne and Reach4 for your help.