Bathroom Venting and 2x4 walls

[dusty12]

I recently bought a 150 year old home in NY where the previous owner seems to have taken a lot of shortcuts. As it stands I think that they did not put in adequate venting. Our toilet clogs regularly, sometimes our laundry room has a sewer smell, and our kitchen sink gurgles when you flush the toilet.

Down the road, I plan to remodel the upstairs bathroom (Currently gutted) and move some exposed pipes into the walls. For now, I am about to fill the shallow attic with insulation, so I am trying to think ahead as much as possible with all of the plumbing prep that I will need to do up there before hand. My goal for now is to set up all of the attic plumbing so that I will be able to move a couple 3" pipes into the wall and have everything vented properly in the future. A couple of the additional challenges are that they are only 2x4 walls, making it difficult to run a 3" pipe, and in the bathroom on the 2nd floor, the sink will be on the opposite side of the room from the toilet and bath, which are closest to the downstairs bath. Below is a rough sketch of how the plumbing is currently set up. I plan to start from scratch with the 2nd floor bathroom.

Can I split the main 3" vent into two 1.5" pipes (above the fixtures) and then reconnect them in the attic, so that I can drill smaller holes through the wall top plates? This would mean that the 3" pipe would terminate at the second floor toilet and the sink, toilet, and shower/bath would each have a 1.5" vent that joined in the attic to exit the roof. Thanks!

 

[Houptee]

If you smell sewer in laundry room the trap is either put in wrong or its getting sucked dry when the toilet flushes. The vent for a trap is after the trap U (weir) so that laundry room you drew has no vent because the standpipe is not acting as a vent. You could T in a AAV in laundry room after the trap to help with the smell.
The Kitchen sink is it a P trap or S trap under the sink now? And is the AAV new and working properly?

 

[Sponsor]

 

[dusty12]

Thanks for the advice on the laundry room. I do think that it is siphoned out every so often.
As for the kitchen (and bathroom) the sinks are both p traps. I would guess that the AAV is fairly old. Aside from hearing gurgling at the sink when the toilet flushes, we haven't had any issues there. Both good tips. Thanks.

My main challenge for now is being sure to put in the proper vent piping in the attic for now, to save myself swimming in fiberglass when I put the upstairs bathroom back together and try to put those other 3" pipes in the walls.

 

[Houptee]

I don't see any vents at all in your drawing other than the kitchen AAV .
You cannot wet vent the 1st floor bath with the wet 3" waste line coming from 2nd floor bathroom. Even tho it goes thru the roof as a vent its a wet vent from the point it drops water.

 

[dusty12]

It’s true, as far as I can tell, the kitchen is the only vented fixture. For now, all of the second floor fixtures are offline, so I think that 3” waste line is currently functioning as a vent. The previous owner took a lot of shortcuts all over the house that I am working my way through. When I replumb the second floor, I am planning to correct the venting issues throughout. For now, I am hoping to set up all the vent pipes I’ll need in the attic and stub them down through the ceiling of the second floor, so I’ll be able to connect to those when I remodel the 2nd floor bathroom and fix the venting on the first floor.

I don't see any vents at all in your drawing other than the kitchen AAV .
You cannot wet vent the 1st floor bath with the wet 3" waste line coming from 2nd floor bathroom. Even tho it goes thru the roof as a vent its a wet vent from the point it drops water.

 

[Houptee]

I had the same project in my 110 yr old house nothing was vented to the current codes but I got it all sorted out.
He probably just replaced exactly what was existing cast iron with pvc and did not add any new vent lines.
You can vent the 1st floor bath with a 1-1/2 pipe up to the attic but you have to vent up from the lav sink trap, and then also need to vent the toilet and shower, there is a rule about how many inches away from the toilet and shower trap the vent can be so possibly you only need one vent 1-1/2" Teed off the 3", then go up the wall and T together with lav vent 42" off the floor min, then one pipe up to the attic where it can T into the 3" that goes thru the roof.
Those are just my thoughts, the pros on here will give you better advice.
Do you know what plumbing code standard you have to follow where you live?
You should be able to pull up the code book online or they have them at the library too.