Shower and lav sharing a vent?

[KRC]

I am hoping that the shower vent will also provide air for the lav.
Right now, the bathroom is serviced by a 2" lateral (single story house) and extends to the washroom (washer/dryer - own vent). I have a 1.5" vent between the shower p-trap (2") and the 2" lateral. Within a foot downstream I want to attache a 1.5" line to connect to the lav (with 1.25" ptrap). I am hoping not to have to vent at the lav as I want to open the wall above for a recessed cabinet. Can't simply go around this as electrical on one side and other side presents other problems.

There is a toilet with its own 2" vent.

I have attached a picture. The "circle" represents the vent pipe going "up" to the attic and out.

 

[MTcummins]

how far from the lav is the toilet vent?

correct me if I'm wrong, better plumbers, but i think that this would be a wet vented lav, which is not legal, but would probably function fairly well nonetheless. if you don't want to put a vent in, why not at least put in an AAV?

 

[Sponsor]

 

[KRC]

Not familiar with these valves - as relates to reliability if installed behind a wall.

 

[MTcummins]

you can't bury it in the wall, you would either leave it inside the vanity under the sink, or put a vent cover in the drywall so that air can flow to the AAV and so that you can remove the cover and get to the AAV. Burying it in the wall is not much different than not having a vent, as it won't have sufficient air draw.

 

[KRC]

OK. Probably not what I need then as I am looking at a hanging/wallmount sink that is very small. There is no cabinet to hide it in...
Maybe someone will comment on sharing the vent with the shower... or are people worried this will create an s-trap at the lav?

 

[MTcummins]

can you get over and physically tie a new vent off the top of a santee in the wall behind the sink into the vent coming off of the shower? i don't remember the fixture units for vents for this setup, but it might be a viable option if that vent can take that many units. again, i'll have to defer to the more experienced plumbers...

 

[Jimbo]

how far from the lav is the toilet vent?

a wet vented lav, which is not legal,?

Au contraire, you could almost say that wet venting is the preferred method to vent a bathroom group. Not where you show it tied in, however.

 

[hj]

The way you drew it the shower "may be" vented, (dependin on how you actually run the pipe), but the sink DOES HAVE an illegal "S" trap. You have a very "unusual" house if the vent cannot be routed around the medicine cabinet opening. We deal with "problems" every day, so we think in terms of solutions for them. Your plan is NOT a solution.

 

[MTcummins]

Au contraire, you could almost say that wet venting is the preferred method to vent a bathroom group. Not where you show it tied in, however.

Could you explain this further? I thought that only a toilet was allowed to be wet vented?

 

[KRC]

Sounds like easiest is to just add a vent at the lav and go up. I guess I can move some electrical on the other stud bay and pipe up along side. Can I joing the 1.5 lav vent and 1.5 shower vent into a 1.5 roof vent or does that now have to move to 2"?

On another note, for clarification, the shower vent is before the shower p-trap. It is the circle in the diagram - and the vent goes up to the roof.

I was worried that the lav might be a s-trap - but given that this is piping into a larger pipe then I wouldn't think a siphon could happen - though I suppose this is load based (i.e. shower running at same time, etc...).

If this is the case, though, how can a bath lav group only share one vent (and not be joining a dry vent from each fixture to a main vent line)? I thought I have seen diagrams all the time where the lav and shower share a single vent - usually at the lav however. The shower ptrap just runs into the lateral feed and the lav is just a few feet away.

In my case, the shower and lav connections in the lateral are 2' awa, and shower vent to lav p_trap is about 3'.

Where would the correct place to tie-in be? At the lav then?

Thanks!

Karl

 

[MTcummins]

if you use a santee at the lav with the vent coming off the top, you will no longer have an S trap.

i don't remember the fixture units for venting, so hopefully someone else on here can comment on the 1.5 vs 2" vent through the roof.

i always vent every fixture (toilet off stack if possible), so can't comment on sharing a vent.

 

[Cacher_Chick]

A wet-vented bath group can only be wet-vented through a 2" lavatory drain, and is dependent on the layout of the fixtures and the direction of flow to the main line.

In this case, the shower could be wet vented through the lav if it were within the maximum allowed distance. Since there is already a vent at the shower, I would leave it alone and just install the required vent at the lav.

The code may vary slightly depending on where you are. Here, we would have 1.5" vents off the shower and lav, but would have to step up to 2" or tie them together in the attic into a single 3" vent before going through the roof. (We are not allowed to have 1.5" vents through the roof due to the possibility of frost closure.)

 

[MTcummins]

interesting. thanks for the info.

i think locally we're not allowed to do this wet vent, though I might have to check into it. I just remember being told by local plumbers that the only wet vent allowed is a toilet venting off the stack. pittsburgh has lots of extra code requirements beyond the standards though, so that wouldn't be too surprising.

I never take my 1.5" or 2" lines through the roof... i hate extra crap coming through the roof. I have some very long 2" vent runs in my house to tie my laundry towards the back of the house to the main stack, which is all the way at the front wall of the house. sure it would have been easier to go up through the roof in the back, but i simply refuse to have extra mess like that

what i was referring to as far as 1.5 vs 2 inch line though is whether a lav and shower can both be combined onto a single 1.5" vent as far as total fixture units. I think they both can, but i never remember the fixture units for vents.

 

[hj]

Given your dimensions, I would run the vent at the sink, but put a T in the vertical line below the floor and run the shower into that.

 

[Jimbo]

UPC 908.4.1 WHERE PERMITTED: ANY combination of fixtures within 1 or 2 bathrooms located on the same floor level may be permitted to be wet vented.

Lots of details about sizing, lengths, etc. see the code book.

 

[MTcummins]

Sounds like lots of exceptions and qualifiers... I think I'll keep going to the extra trouble of venting every fixture, until I run into a situation where its not feasible to do so, then I'll see if Pittsburgh will allow such a thing. We have a TON of extra code beyond the standard code, such as requiring 2 traps and 2 vents for a double bowl kitchen sink. Everyone on here thought I was nuts when I posted that, but its what we're required to do.

Good to know that it is generally legal though. So to be clear, the standard setup would be to have the shower 2" drain go past the lav with its 2" drain dropping into it, and the lav's 1.5" vent is sufficient to carry both, as long as its within a certain distance? or is 2" vent required for this application? and you would generally need this wet vent to be w/in about 4 feet of the shower trap, or is that a different distance? obviously this is simplest senario, and there are a lot of exceptions etc, just wondering what the basic allowance is.

I don't have the UPC, I use the IRC in most of my work, and I don't think it gets down to that level of detail on plumbing code. I only get the very basics in there, but I always want to know what my subs are doing and that they're doing things right. The more I know, the less they can get away with and the better my work is overall

Thanks.

 

[Cacher_Chick]

You have the idea... the thinking behind wet venting through the lav is that it is only a 1 dfu fixture, so if you drain it with a 2" line, there will always be room for free flow of air through the wet section. An entire bath group can be vented through a 1-1/2" vent.