Plumbing Plan / Layout advice needed!

[Hwmfh]

Hi All

Glad to be here, and looking for some advice regarding a plumbing layout/plan.

A little backstory, we brought our house a few years ago pre covid. The bathroom had been gutted/back to studs by the previous owners, we purchased the house knowing that we would be taking on a bathroom reno at some point. After cleaning up/working on other areas of the house I'd love to get this bathroom done so my kids can have a bath and not just showers! Its a constant complaint in our house it seems!

The house is in CA and is on a slab foundation.

I'll need to dig up the slab to lay new plumbing so want to get it right before i make any cuts and would love to keep this thread or perhaps another updated with progress.

My suggested layout/plan is below. I guess my main questions would be. Would this work or am I over complicating it. Wasn't sure if i need the dry vents for the tub/shower or if this could be a wet vent off the sink?

 

[John Gayewski]

The pink vent for your toilet and shower aren't correct they would need to be vertical (45° minimum) while beneath the concrete. .

California is upc so for a horizontal wet vent your toilet needs to be the most downstream (first to drain into the branch).

 

[Sponsor]

 

[John Gayewski]

A horizontal wet vent for this would look something like this. But your trap arm lengths might be hard to achieve.

 

[John Gayewski]

A conventionally vented system with one wet vent for the toilet via the lav would look something like this.

 

[wwhitney]

In the last diagram you could also wet vent the tub via the shower and thereby have one less dry vent takeoff.

If the vanity and the WC were swapped, it would be possible to wet vet everything from the vanity without much trouble. As is, the vanity would have to cross over the WC and it would be tricky to comply with the 5' length limit on the shower and tub trap arms, and the 6' length limit on the WC fixture drain.

Cheers, Wayne

 

[Hwmfh]

Wow, thanks for all the responses! So it seems that horizontal dry venting isn't a thing under slabs.

I think the vanity needs to stay put, its right next to the door and I'd rather that be the first thing you see as you enter rather than a toilet. The bathroom is pretty small so I might be able to make the horizonal wet venting work, however that being said it looks like i'll be aiming for something like the last picture. Per Wayne's comments if i can wet vent the bath from the shower that would look like so right?

I'll grab some shots of the room and try and update the thread as i go!

 

[John Gayewski]

Wow, thanks for all the responses! So it seems that horizontal dry venting isn't a thing under slabs.

I think the vanity needs to stay put, its right next to the door and I'd rather that be the first thing you see as you enter rather than a toilet. The bathroom is pretty small so I might be able to make the horizonal wet venting work, however that being said it looks like i'll be aiming for something like the last picture. Per Wayne's comments if i can wet vent the bath from the shower that would look like so right?

View attachment 83917

I'll grab some shots of the room and try and update the thread as i go!

Yep that'll work

 

[wwhitney]

Per Wayne's comments if i can wet vent the bath from the shower that would look like so right?

To wet vent the tub from the shower you need the vent to come off the shower trap arm before it joins the tub trap arm. [Or vice versa to wet vent the shower from the tub.]

Also if you want to pull a vent off a trap arm and keep the drain horizontal, you can do that with an upright combo. As opposed to a san-tee, where the drain turns down as you pull the vent off the top.

Cheers, Wayne

 

[Hwmfh]

Once again thanks for all the replies, I got time today to get in the bathroom check out the current plumbing placement, and measure things out. I'm starting to lean towards the wet venting suggestion above due to 2 reasons.

1. The room is relatively small
2. There is already a vertical vent in position C from the previous Lav.

Based on CA code it seems the wet vent max length is 60 inches on a 2inch pipe, my understanding based on the suggestion above is that this section from the Lav to the tub (A to B) would need to be 60 inches or less correct?

 

[wwhitney]

On the 60" limit for a 2" trap arm, for the tub (if you use a 2" trap), that would be the distance from the tub trap outlet to point B. The length of the wet vent itself, from B to A, is not limited.

The vertical vent at C, if it's a dry vent, you can't use it to vent the WC like that. Because you'd have a horizontal dry vent below the floor. If you dry vent a fixture (WC), then the dry vent has to come off vertical (at least 45 degrees above level) and stay vertical until at least 6" above the flood rim. When the lav was draining into the vertical, it was a wet vent, so those particular limits didn't apply.

The WC vent needs to be within 6' of the closet flange. So if the drain length from the flange (not shown) to that final wye to the left of B is under 6', you could wet vent the WC via the lav, just like the tub and shower. To do that the wet vent (drain) would need to be enlarged to 3" starting at point B.

Cheers, Wayne

 

[Jeff H Young]

Having vent at "C" might or might not help , in any case you need a vent at the lav and it needs be minimum 2 inch if serving the W/C so the lav might likely be able to use the old vent if its 2 inch or greater

 

[Hwmfh]

Hey all

Firstly thanks for all the responses, its appreciated

a much delayed response but life seemed to get a bit hectic the last few months so this project got left behind. However I had plumber locate the main sewer line so i can prepare to dig in the coming weeks.

So I've revised the plans a bit and looking for some additional feedback, Ideally I'd like to keep the toilet vented by itself, the main reason for this being if i ever wanted to separate off the lav, shower and tub for greywater in the future.

so a few questions, from the above comments it seems like there is no limit on the wet vent, just the trap arm going to the wet. In this case I could get both the shower and bath tub under the 60" limit for a 2 inch pipe.

1, Can I use a three way Wye where the three meet?
2. When the three converge would I need to upsize this section (green) to 3"?
3. The main sewer line is around 26 inches deep, i plan on doing the 3 fixtures closer to the surface would i be able to use a vertical drop with a long 90 at the bottom here to bring it down to the mainline?

Thanks again!

Stu

 

[wwhitney]

1) Probably but it's a bad idea. Two separate wyes allow you to adjust the slope of the side branches individually. The ideal "double wye" shape would not actually be flat, the two side branches would be sloped up relative to the barrel.

With a flat double wye, the best case is that you get the two side branches level with each other (if one is high, the other is low with reduced slope). If you achieve that, the side branch slope is only 70% of the barrel slope. So you'd need to have the barrel sloped at least 3% to keep the side branches at least 2%.

Because of those tricky details, I've read that some jurisdictions prohibit the arrangement.

2) No, 2" will suffice for the green portion in the drawing.

3) Yes

Cheers, Wayne

 

[Hwmfh]

Hi Wayne

Thanks for the response, yeah I understand what you're saying about the "double wye"

I believe what you're suggesting with the individual wyes would look like below from a birds eye view?

 

[wwhitney]

Almost--since the lav is the wet vent, it needs to be the upper wye in your diagram, so you don't have two unvented trap arms joining each other.

Cheers, Wayne

 

[wwhitney]

Also, if you are going to use a 2" tub trap arm, you need to use a 2" tub trap.

And in case it matters, the dry vent portion of the lav vent can be 1-1/2" instead of 2" if desired. A 1-1/2" dry vent is good for 8 DFU under the UPC. The wet vent portion has to be 2" as that's the minimum UPC wet vent size. In other words, the lav san-tee could be a 2 x 1-1/2 x 1-1/2 fitting.

Cheers, Wayne

 

[Hwmfh]

Thanks Wayne, Understood, so the Lav would need to be in the middle like so?

When it comes to the ptrap/drain for the tub, the tub has a 1 1/2 inch connection (freestanding) can I use a reducer at the trap opening to reduce it down to the 1 1/2? Or could i just run this entire section as 1 1/2 to the Wye when it upsizes to 2 inch?

Thanks again

 

[wwhitney]

Yes on the diagram.

On the tub trap you have two options: use a 1-1/2" trap, a 1-1/2" trap arm, and keep the trap arm to 42" or less; or use a 2" trap, a 2" trap arm, and keep the trap arm to 60" or less. The trap arm is from the trap outlet to the wye where the tub gets wet vented.

Yes, with a 2" tub trap, you would use a 2x1-1/2" reducer on the trap inlet to connect to the 1-1/2" waste and overflow.

Cheers, Wayne

 

[Jeff H Young]

The double wye looks real clean and simple but for reasons Wayne mentioned I dont even try double wyes they are harder to find from some places if you buy one and wind up not using it it will sit in your box or gunny sack or stored somewhere forever till you need it . Sometimes I order up stuff a certain way go out to job and wind up changing way I plumb it, more like often that happens lol...