What size vents?

I'm trying to figure out if my vent sizes are correct.

Right now i have a 2" hole in my roof, and a 3" hole in my basement floor.

I will have a double sink vanity, and the double fixture fitting has a 1.5" vent out the top, and a 2 in drain on the bottom. This will meet my 1.5" tub drain in a wye, which will continue as 2" until it meets another wye with my 3" toilet drain. The toilet has a 2" vent. The tub has a 1.5" vent.

Here's the thing - my vent hole in the roof is directly over the sink vent. The tub and shower vents are across the room. How would you connect all these in the attic? If they were all the same size i'd just have flipped some sanitees over. Should i just use a reducer in the wall, upside down, and upsize my sink vent to 2"? Or do i get one of those 2" side and bottom, 1.5" top sanitees and flip it upside down, so its 2" after that point in the attic? How would you do it?

Are those vent sizes correct anyways?

stuart in pa

Most homes require the same venting through the roof as what you have going out.
If you have a 3" leaving the home, then you would use either a single 3" vent, or a composite to make up the area of the 3".
That would be two 2" vents and one 1.5" vent.
A 4" drain would need four 2" vents.
How many vents are through the roof now, and what size?

I have one stack in the kitchen. It goes into the basement floor at 3", out the roof as 2". There is a double kitchen sink and a laundry tub on it.
I have one stack in the half bath. It goes into the basement floor at 3", out the roof as 2". There is a toilet and a sink on it.
I have one stack for the full bath. It goes into the basement floor at 3", out the roof as 2". There is a double sink, toilet, and tub on it.

This is how the house was when i bought it. I have not added any holes in my roof or basement floor.

When i say its "three inches" going into the basement floor, they used to have 3" cast iron cemented into what appears to be 4" "soil bore" terra cotta. I use donuts from fernco that are 4 inch "soil bore" x three inch pvc now instead of the cement job they used to have. I don't know what happens after they go into the basement floor, i assume its 4" terra cotta the whole way out.

Edit: the laundry tub is technically vented by an AAV which i added.

Another edit: upon further review, my 4" donuts actually go into the "bell" of the terra cotta, and i think it may be 3" terra cotta. That would make my vent situation correct, yes?

Ok, one more problem...there is a damn electric box (other side of wall) right in the way of where one of the arms of the double fixture fitting would go. So tell me if this is fine to do instead.

That works too.

Is is acceptable if all that piping is 1.5"? Do you have to "upsize" the pipe when two 1.5" drains meet like they do in the middle?

It needs to be 2" where the two meet.

I have never seen 3" terra cotta pipe. you can use a sanitary tee instead of the combo. You have not changed the fixture load, so 1 1/2" should suffice.

hj said:

I have never seen 3" terra cotta pipe. you can use a sanitary tee instead of the combo. You have not changed the fixture load, so 1 1/2" should suffice.

Click to expand...

Terry said:

It needs to be 2" where the two meet.

Click to expand...

Well, i was thinking you couldn't stack sanitary tees, but knowing that, i have plenty of space to put in 2" sanitary tees with 1.5" arms, so i'll use the 2" drain and vent there. Works for both of you?

Newest question. Can i vent my toilet like this?



The reason i ask is because the vent goes "horizontal" until its under the wall, and i thought that wasn't allowed. What are the "exceptions" to the horizontal rule, besides "above the flood rim"?

I'm in PA and we use the IPC. The old toilet was sitting DIRECTLY on top of the 3" stack - so at best it was wet vented through the lav. Am i wasting my time even venting this thing (according to IPC)? Can it be a 1.5" vent or does it have to be a 2" vent?

That pic has come up several times before. It is not a legal way to do it.

Since you are under IPC, there is no limit on the distance with regards to venting toilets. Probably your best bet is to wet vent the entire bathroom through the lav.

My lav drain is going to be running perpendicular to the joists, underneath them. The toilet drain is going to be running parallel to the joists, between them. I don't see how i can vent through the lav if its drain is lower than the toilets drain...thoughts?

nukeman said:

That pic has come up several times before. It is not a legal way to do it.

Click to expand...

Can someone tell me why this picture is illegal?



Is this person's setup also illegal?



If you can't do either of those, how do you vent a toilet in the wall behind the toilet when the drain goes the opposite direction? You can't use a wye and a 45? How do you vent toilets in basements them when you HAVE to run horizontal underground? And if you can "wet vent" horizontally, why can't you "dry vent" the same way?

As you mentioned, the problem is that it is a flat vent below the flood rim. A flat dry vent can get clogged up with "stuff" over time and you would never know if it is clogged. A wet vent can be flat as it gets flushed out with use. You also would know if it was clogged as the lav/shower wouldn't drain.

You say that the one set of lines will be under the joists. Is there a crawl space or unfinished basement below? It might be helpful to make a drawing of the bathroom layout and where everything is going might give us some idea on how you might connect everything.

Edit: Here's one of the threads talking about a similar pic.

https://terrylove.com/forums/showthread.php?38211-Does-this-toilet-vent-look-OK

I haven't drawn up a picture yet, i'll try to when i get a chance. Its a 3" toilet drain running between some joists so i can finish the ceiling, meeting with a 2" drain that is running just under the joists, perpendicular to them. IE, the toilet drain is higher than the sink/tub drain. Let me get on that pic...

EDIT: quickly done. I hope you can see why i have to vent behind the toilet...that left wall with the two joists close together prevent me from using it. So is this possible? Keeping a toilet drain between the joists yet draining behind the toilet?

On the lav drain, are you going to box that in or drop the entire ceiling? It may be possible to route this line through the joists as well. At any rate, the 3" line is going to eventually connect to that 2" line before going down the stack. At this point, the toilet will become vented.

It might be helpful to show the bathroom from a top view. Show where everything is going, the direction of the joists, and how you plan to run the drain/vents and what sizes you plan on using. This way, others can tell you if what you have is good or how a better way might be done. Often, you have to think outside the box a bit. People often have this flat vent problem when trying to layout for a shower. Instead of running the vent right off the trap (which would normally cause a flat vent), you can often run the drain to the closest wall and then vent. This could be 5'-8' assuming 2" pipe and depending on whether IPC or UPC. The plumbers on here do this kind of stuff everyday. However, they are not there to see what you have and often don't have the time to guess and draw something for you. However, if you take some time to draw up what you have and what you plan to do (and possibly add a pic or two of things that might be in the way of your plumbing), the guys on here are pretty good about telling you if it looks good and how it could be improved. There may be even better ways to run everything, but they might not be able to tell since they are not there to see it.

The lav drain will be as close to the joists as possible and will be boxed in, it actually will be running right next to an I beam that needs boxed in anyways, i'll box them in together.

I guess i'm thinking the toilet line won't be vented, but the main line will by the lav drain, so that's good enough, because the toilet line meets up with the same stack?

I didn't want to drill through any of the joists - they are 2x10s, fully sistered so we can put in 18" travertine. That would be a pain to cut through, plus, i'm concerned about weakening the floor with a line of holes, even if allowed by code. Then you're cutting small lengths of pipe, tons of couplings, etc. That was the original plan until i decided to extend the box of the ibeam instead.

Again, i'll try to get a drawing up as soon as possible...