I am working on installing a clawfoot tub into a c. 1915 building with exposed 4" cast iron drain/vent pipes. The upstairs bathroom it's going in used to have two side by side toilets, as shown in the attached image (viewed from the bathroom below). The tub will be over where the left hand drain pipe is, the toilet will stay over the right hand pipe, and the far right vertical pipe goes up through the roof as a vent pipe (and down to the sewer below).
I'm a novice, but am trying very hard to do everything in this bathroom myself (including replacing the entire floor last week). My plan was to come down through the floor with the 1.5" tub drain and put the P trap below the level of the existing iron pipe and then go back up and down into the iron pipe using a rubber doughnut, like this: http://www.yourepair.com/howtos/images/kitchenbath/cast-iron-hub-donut.jpg
I thought this was the best solution, as you wouldn't see the rubber doughnut from below (I'm trying to preserve a somewhat clean "original" appearance for the exposed piping downstairs by avoiding rubber sleeves, plastic piping, etc). But, I'm having trouble finding a doughnut that adapts from 4" ID pipe to 1.5" OD pipe. I've thought about drilling a hole through a large rubber stopper...
Anyways, the larger concern is that after reading through some other forum posts, I'm realizing that my idea will basically resemble an "S" trap, which can be a code violation because of the issue with losing water in the trap due to suction issues. Should I be concerned about this, and is there any similar solution that won't have the same issue? My original thinking was that because I was adapting relatively small pipe into a much bigger pipe that had it's own vent that this wouldn't be an issue (plenty of relative airflow), but I have doubts now and could use a second opinion!
Any thoughts would be very much appreciated...I'd like to do this as "right" as possible. There is also a sink drain on the other side of the room, but because of it's layout with relation to beams/vents/windows, it would be a real challenge to plug into that as well. This old toilet drain is right where I need it to be!
I'm a novice, but am trying very hard to do everything in this bathroom myself (including replacing the entire floor last week). My plan was to come down through the floor with the 1.5" tub drain and put the P trap below the level of the existing iron pipe and then go back up and down into the iron pipe using a rubber doughnut, like this: http://www.yourepair.com/howtos/images/kitchenbath/cast-iron-hub-donut.jpg
I thought this was the best solution, as you wouldn't see the rubber doughnut from below (I'm trying to preserve a somewhat clean "original" appearance for the exposed piping downstairs by avoiding rubber sleeves, plastic piping, etc). But, I'm having trouble finding a doughnut that adapts from 4" ID pipe to 1.5" OD pipe. I've thought about drilling a hole through a large rubber stopper...
Anyways, the larger concern is that after reading through some other forum posts, I'm realizing that my idea will basically resemble an "S" trap, which can be a code violation because of the issue with losing water in the trap due to suction issues. Should I be concerned about this, and is there any similar solution that won't have the same issue? My original thinking was that because I was adapting relatively small pipe into a much bigger pipe that had it's own vent that this wouldn't be an issue (plenty of relative airflow), but I have doubts now and could use a second opinion!
Any thoughts would be very much appreciated...I'd like to do this as "right" as possible. There is also a sink drain on the other side of the room, but because of it's layout with relation to beams/vents/windows, it would be a real challenge to plug into that as well. This old toilet drain is right where I need it to be!