Toilet + sink plumbing plan: please review -- trying to decide between two plans

Hi everybody,

First of all: what an incredible forum this is!

In planning the PVC plumbing for the toilet and sink in our new bath room, I have the following questions -- see the attached image for reference:

* Does the toilet drain need a separate vent from the sink drain, or can I vent the toilet through the sink drain? I assume I have to vent separately, but I am not 100% sure.

* When venting the toilet separately, does this vent really have to connect to the toilet drain through a Wye? Can I not just use a sanitary T for this? I am asking this because in a Black & Decker plumbing book they connect vertical dry vents to drains through sanitary T's. They only use the Wye to connect the sink drain into the toilet drain.

Little bit of background: the plumbing plan I drew up only shows the hidden PVC portion. To this, I will connect a wall-mounted Duravit Darling toilet with Geberit water-tank onto the 3" drain, and a porcelain vessel sink with chrome P-trap to the 2" drain. The combined 3" drain connects to the existing waste line.

I really appreciate any feedback you can give.

Thanks so much,

- Erik

the bottom one is correct as far as the wye goes...even though your tee'ing off to a vertical vent..it's still part of the waste, and you cant have the san-tee on it's back.

Thanks for your quick response... Yeah, that's how I also understood it from studying the code. Confusing though that Black & Decker's plumbing book does show these sanitary T's on their backs.

As for my other question, "Do I need to vent the toilet separately from the sink?", it looks like I don't have to when looking at http://www.iapmo.org/common/ROP2004/upc04rop/preprint/ch9.pdf.

From UPC Code 908.1 I deduct that in my case I can wet-vent the toilet through the sink-drain, as long as I use a 3" diameter pipe for the wet-vent/sink-drain (908.2).

Can someone confirm that?

Thanks,

- Erik

Oops, one minor error in the drawing: the horizontal trap arm of the sink drain is not 2" in diameter, it's 1 1/2 ". The vent for the sink is planned to be 2".

With the sink drain trap arm being 1.5", can I wet vent the toilet through a 2" pipe, or should that be 3" to meet UPC?

- Erik

you can't wet vent horizontally...where is the a wet vent anyways?

No no, not planning to wet vent horizontally. The vent coming in horizontally is a dry vent.

I would just prefer to vent the 3" toilet drain through the vent that's already venting the sink. The couple of feet of vertical pipe between the sink's trap arm and the horizontal toilet drain would be the vet vent for the toilet.

I believe that's allowed, judging from the UPC paragraphs I referenced, but I am wondering whether that little bit of vertical pipe needs to be 3" or whether I can leave it 2".

- Erik

pipes

Depending on how long the sink arm is it may have to be 2" and the vent for the sink only has to be 1 1/2". If your lavatory is close enough to the toilet, you can eliminate the sink riser and install the tee in the toilet vent, in most cases as long as wet venting is allowed in your area.

ok ...now i got ya...i was confused at first because looking at the drawings i saw no wet vent. Yeah anyways..as long as you can meet the required distance for the 3" which is 6' to vent, and as long as wet venting is permitted in your area..i dont see why not. You can also do what hj said, by removing the sink riser, and teeing into the toilet vent, again assuming the lav is within the required distance for the 2" (5' to vent) then the toilent vent becomes the wet vent

Plan C

Right, that makes sense -- see new rough-in diagram below.

The trap arm of the sink will only be about a foot. I can meet the 6 ft requirement for the toilet drain; in fact I can place the vent such that it will tap into the toilet drain at about 5 ft, making the sink trap arm a foot and a half maybe two feet.

Studying my plumbing books and Tauntan Press plumbing code overview, I got the impression that the UPC is the most strict code. With my PLAN C I believe I am meeting the UPC. Does this not automatically mean that I meet any local requirements? Could it be that despite meeting UPC it's not allowed here to have the two feet or so vertical run of 2" wet vent between the sink and the toilet drain?

I'll try to look this up on the Cambridge MA web site...

- Erik

yep ..unfortunately, the call on the wet vent is up to the ahj. Some places allow it others dont. By the way ..what software is that you're using?

What is the AHJ?

I just drew this up in Photoshop. If you look at this page: http://www.staffassoc.com/dpfonts/sampfont.pdf , then you'll see an example of a PVC Pipe font. I zoomed in on this page, took some screen dumps, imported those in Photoshop and derived all the shapes from that. I made the different pipe diameters to scale, and had to do a bit of cutting and pasting to get things like sanitary T's (since those aren't part of this font sample). I'm happy to share the file with you if you're interested.

- Erik

the Tee issue

I dont mean to staart a big debte here but it looks to me like either way the guy is running that system will work out just fine..and dnady.

Who says you cant have a horizontal tee laying on its back??? I see it all the time.

I have always understood it to be you cant have a horizontal tee laying on its SIDE, due to the fact if their is very little fall in the system, sewage in high demand moments, could run back up that tee fitting???

I see that all the time too.

Somebody correct me if I am mistaken.

tee

You must have very lenient inspectors. Our inspectors do not permit it because a sanitary tee does not have enough "sweep" to contribute to the downstream passage of the water. Their feeling is that that water and waste is going to drop straight down and splash on the back side of the pipe. Even though this installation does not have any water in it, the ruling is that any piping below the overflow rim of the fixture has to be installed as if it would have water flowing through it. And if there were a cleanout in the verical pipe, which might be necessary depending on the rest of the piping and the bathroom's location which we do not see, then it would definitely have to be a sweep fitting.

Tee

For persons with a similar situation where IPC is enforced "Plan A" would work fine, as would "Plan B" and "Plan C". The minimum sizing requirements for "Plan C" under the IPC would allow a 1-1/2" wet vent, 1-1/4" lavatory drain, 1-1/2" dry vent.

I'm not very familiar with the UPC, but the IRC does allow the use of a sanitary tee on its back for connecting a dry vent to a horizontal drain. They also allow horizontal wet venting. As mentioned I believe the UPC is more strict in most areas, and they like to use the term AHJ (authority having jurisdiction).

ipc

It may not be that the UPC is more strict in some areas, but rather that the IPC may never have seen anything it did not like.

Oregon allows santee on it's back to serve as a vent with any fixture it connects to.

But your can not use a santee on it's back if the vertical rise will be used in a wet vent set up wet, when wet vent is needed then wye combo will be used.

beating a dead horse

I thought that either of these plans would work out just fine.

it aint going on the space shuttle ,

so why don't you just flip a coin