CanAmSteve
New Member
Hi all - first post here. We have a small cottage in Maine and my better half has decided we need another bathroom and bedroom on the ground floor, which was originally a garage/workshop.
I have access to the main DWV stack in one corner and I would like to add the bathroom there. I will have to build the floor up a bit anyway (about 6") to account for the "step" between the concrete footing and walls. I have a 9' ceiling, so no problem going up a bit.
My question is whether the 2" shower drain can be cut into the stack on the bottom, and then a rear-flush toilet drain above that? If I cut off the existing 4" stack just above the slab and add a 4X4X2" wye for the 2" shower drain, it will be *just* possible to drain the shower (using a low profile trap) and tub into the stack. The shower and tub will be on the other side of the room, so even raising the shower pan another 6" leaves the shower drainline only 9" or so above slab. The drain has to run the "long" way around the walls (to avoid the door) pick up the tub drain and then continue to the stack. It is about 12' from the shower drain to the stack. At 1/2"/ft slope, that's 6", so it is doable, but only if I can put (ideally) a 2" drain connection *below* a 4" wye for the toilet.
I am not sure if this is permitted or not. The concern would be that the toilet flush water could be forced into the shower drain line due to their proximity . The toilet drain centerline is 8" above the finish floor, so it will be about 15" above slab. Depending on the connection used below for the shower/tub drain, this would allow for about 10" of vertical difference between the toilet drain and the shower/tub drain.
Alternatively, I *could* insert at 4X4X3" wye at slab level. I could chisel out enough concrete to give me space to recess the coupling into the slab, which would then give me a toilet drain "sweep" with a centerline about 8" above slab. But my shower drain is only 9" above slab and 12' away - even at 1"4" slope, I need 3" of drop.
I suppose the simplest solution if the sink/shower drain must be above the toilet drain is to just build up the shower and tub drain heights further to allow their drains to be above the toilet drain. The shower/sink drain could be tied into the horizontal run of the toilet at its lower level near the stack. I'd like to avoid having to go to a pumped setup, and breaking up the concrete is a last resort. On the plus side, I have easy access to the existing venting (3" vertical) and as mentioned, plenty of space above.
Executive summary - can a 3" toilet drain discharge into a 4" vertical waste stack above a 2" sink/shower drain, and if so, what restrictions are there on spacing and fixtures used? Would it be acceptable to discharge the sink/shower into a wye at floor level with the toilet discharging into a sweep above? Many thanks
I have access to the main DWV stack in one corner and I would like to add the bathroom there. I will have to build the floor up a bit anyway (about 6") to account for the "step" between the concrete footing and walls. I have a 9' ceiling, so no problem going up a bit.
My question is whether the 2" shower drain can be cut into the stack on the bottom, and then a rear-flush toilet drain above that? If I cut off the existing 4" stack just above the slab and add a 4X4X2" wye for the 2" shower drain, it will be *just* possible to drain the shower (using a low profile trap) and tub into the stack. The shower and tub will be on the other side of the room, so even raising the shower pan another 6" leaves the shower drainline only 9" or so above slab. The drain has to run the "long" way around the walls (to avoid the door) pick up the tub drain and then continue to the stack. It is about 12' from the shower drain to the stack. At 1/2"/ft slope, that's 6", so it is doable, but only if I can put (ideally) a 2" drain connection *below* a 4" wye for the toilet.
I am not sure if this is permitted or not. The concern would be that the toilet flush water could be forced into the shower drain line due to their proximity . The toilet drain centerline is 8" above the finish floor, so it will be about 15" above slab. Depending on the connection used below for the shower/tub drain, this would allow for about 10" of vertical difference between the toilet drain and the shower/tub drain.
Alternatively, I *could* insert at 4X4X3" wye at slab level. I could chisel out enough concrete to give me space to recess the coupling into the slab, which would then give me a toilet drain "sweep" with a centerline about 8" above slab. But my shower drain is only 9" above slab and 12' away - even at 1"4" slope, I need 3" of drop.
I suppose the simplest solution if the sink/shower drain must be above the toilet drain is to just build up the shower and tub drain heights further to allow their drains to be above the toilet drain. The shower/sink drain could be tied into the horizontal run of the toilet at its lower level near the stack. I'd like to avoid having to go to a pumped setup, and breaking up the concrete is a last resort. On the plus side, I have easy access to the existing venting (3" vertical) and as mentioned, plenty of space above.
Executive summary - can a 3" toilet drain discharge into a 4" vertical waste stack above a 2" sink/shower drain, and if so, what restrictions are there on spacing and fixtures used? Would it be acceptable to discharge the sink/shower into a wye at floor level with the toilet discharging into a sweep above? Many thanks
