I'm helping my daughter buy a house and we have an affordable candidate, but the upstairs bath is clearly not up to code and I'm wondering if we can work around it.

The two-story house was built in 1960 with one full bath on the main floor vented with a 3 inch cast iron pipe through the roof. At some later time, a bath was added in a second floor dormer right above the original bath. There are no roof penetrations associated with the second floor bath and the 3 inch cast pipe is too low to be venting the newer bath. In addition, there is no p-trap under the lavatory!

The toilet works fine and the stall shower seems to drain well. If I fill the sink and let it drain quickly, the water in the shower drain pipe moves up and down. Flushing the toilet does not do this. I imagine they are draining the new bath through the original 3 inch stack, which I think invalidates the stack as a vent for the lower bath, but doesn't seem to really affect any functioning. It seems to me that if I put a p-trap under the lavatory with an AAV, I'll have a reasonable set up until we do major renovations, opening walls, etc.

Do you think this might work? Also, the house is in Mass and I'm not sure if AAVs are allowed.

If I fill the sink and let it drain quickly, the water in the shower drain pipe moves up and down.This is because the sink'
's attempting t6o vent through the shower. Venting the upstairs lavatory may vent the upstairs bath but since you're using the downstairs bath vent stack as a stack vent you'll have to vent the downstairs bath as well, Massplumber can answer your question about AAv's. Good luck, Tom

Toilets have P-Trap built in. So no need to do anything with the toilet. As Tom said, water in the shower drain moves bcs there is no vent on the sink. Overall, if it works OK now, don't do anything. However, if you like things done right, you will have to deal with it later...

This is what I would do: Once you start remodeling, you add vent to the sink and bring it through the roof. That should take care of venting for upstairs bath. If the 3" drain is connected to the stock vent than you should make that connection below the 1st floor bathroom. Bring 3" main drain from upstairs bath under the house and reconnect with the main sewer pipe there.

Hope that helps. Milo

Hi Dclynch

Certainly sounds like they used the vent stack from the first floor as the waste stack for the 2nd floor bathroom... and no, AAVs are not allowed in Mass... ;)

Of course, since using a vent stack as a waste stack is illegal, I'd say installing an AAV under the sink drain for now will be better than nothing, right?

Mark

This is amazing, guys! Three great replies in such short order. I'll go with the AAV under the sink now and be back for more help in a couple of years.

Thanks again.