Connecting to a soil stack

lanthoma · Mar 12, 2010

1. Can a toilet sit at the top of a soil stack (no bends between the flange and the stack)? It seems like this would be OK, but I never see it done this way.

2. When tying a drain from a tub or sink into the soil stack, is it OK to use a wye instead of a san-T? In another post (https://terrylove.com/forums/showth...om-toilet-into-stack&highlight=soil+stack+top) it was stated that you could only do it with a toilet, but I think that it should be OK if the tub & lav have their own vents.

3. When combining two 1.5 in vents to go through the roof, what pipe size should be used after combining.

Thanks,

Lance

Jc60618 · Mar 12, 2010

1.Are you trying to install a bathroom in the attic? The soil stack must extend uninterrupted thru the roof. If you install a toilet at the top of the stack with out any bend you will omit your entire venting system. The stack must terminate above the roof. What you are proposing is to cut the soil stack before it exits the roof and installing a toilet is prohibited.
2. A lav and tub cannot be tied in like that. That wye application only works for toilets.
3. Depends on your local code. In Chicago you need 4" thru the roof.

Can you post pics of what your trying to do.

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NHmaster · Mar 12, 2010

Are we talking say a toilet sitting on a 3" pipe with a vertical drop of one story or more? If so it would be very strange indeed but IPC code says distance from toilet to vent is unlimited so it there's a vent in the same house I can't see why you could not do it. One thing is sure. That stack ain't never getting plugged.

lanthoma · Mar 13, 2010

Thanks guys... I've included some pictures to clarify what I was trying to say. It's a main floor bathroom remodel (second picture) and I'm keeping all the fixtures in the same location, just replacing cast iron with PVC and adding vents (nothing was vented before). I'm trying to vent the toilet through the lav and the tub will have its own vent. Currently the toilet sits on a 3" pipe that drops through the basement and ties to a 4" line which catches a kitchen, laundry, and bathroom (first picture - that project is done!)

The reason I ask about using a wye is that the tub and lav come in at similar levels, but different angles to the stack. If this configuration is not allowed, is there another way to do it?

Thanks,

Lance

NHmaster · Mar 13, 2010

That you can not do because when the toilet flushes it blocks the drain and vents for the lav and tub

Jc60618 · Mar 13, 2010

Why cant you install a sanitary tee and 90 to pick up the toilet?

lanthoma · Mar 13, 2010

I thought it seemed a little odd to have the toilet like that. I can put in a 90 and sanT - it just means I have to break some concrete to move the stack over a bit. Right now the toilet is directly above the soil stack. Does the toilet tie-in go below the lav drain and above the tub drain as drawn? And is that wye to the tub OK or does it need to be a sanT?

-Lance

Doherty Plumbing · Mar 13, 2010

You need to tie the tub in upstream of the toilets connection to have a proper wet vented system. But you guys DO have DIFFERENT rules for wet venting then us Canadians so I can't say for sure that it would be acceptable under your code.

Edit: Nm I just looked that picture a little closer. The way you have it now would be acceptable under Canadian code because you are simply wet venting the toilet through the lav and the tub is separately vented.

Jc60618 · Mar 13, 2010

You can use a double wye below the sanitary tee to pick up the tub and lav. Another option depending on your code is to get a 3x3x3x2 sanitary tee with right/left hand inlets to pick up your entire bathroom. You can also try to offset the stack with two 45 degree elbows instead of breaking up the floor and moving the stack. The drawings I provided would work under the Chicago code however check your local code.

hj · Mar 13, 2010

Absolutely NOTHING wrong with the second picture. A vent only starts working AFTER the flow has passed the vent connection, not while the water is flowing. As long as a fixture has its own vent you can connect it to the system any way you feel like it. Just do not drop too far out of the toilet before making one of the connections or the toilet will flush so strong that it will suck everything within 6' of the toilet down the drain. What is the purpose of the first picture, however, since it seems to have NOTHING to do with the job you are asking about?

lanthoma · Mar 13, 2010

Thanks for the drawings, JC. I'm trying to avoid running a vent behind the toilet due to some joists that are in the way. This forces me to wet vent the toilet through the lav... I do like the idea of offsetting the stack.

To avoid the super flush problems that HJ and Peter were talking about, I guess the layout in post 7 is better. It sounds like it will work in Canada... are there any problems with it under IPC? Would it be better to bring the tub drain into the stack before the toilet?

You're right, HJ, I probably don't need that first pic in post 4. It was just to show the rest of the plumbing downstream of the bathroom in case it mattered.

hj · Mar 15, 2010

IF the vent connection is NOT extremely remote from the toilet any of the methods will work without "super flushing".

Connecting to a soil stack

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