Is it possible to branch the toilet to an old cast iron pipe?

Hello community,

I want to renovate my very small bathroom (have it renovated) and need every centimeter for this.

Unfortunately, I have old pipes in the wall. The toilet drain is also about 40 cm away from the wall. Is it possible to install a wall-mounted toilet and connect the "new" drain directly to the cast pipe (see attachment)? The cast pipe (built in 1970) has a diameter of about 11 cm.

Best regards
Zwusel

In principle, that works quite well. Cut out a piece, insert a branch, seal with collars. I found a similar construction at my place. It looks professional. However, you will get other answers here on how to do it properly.

A wall-mounted toilet also requires the wall with the flush tank. This typically has a depth of just over 20cm. Conveniently, the drain to the downpipe is also located in it. It feels absolutely reasonable here, although I cannot assess the sentence "I need every centimeter for this." Maybe there are (more expensive) shallower variants, one has to check.

In principle, you can connect new HT pipes to old cast iron pipes. The pipe, built in 1970, was formerly called GA or LNA pipe (today SML). You can get adapters for this to today's used HT pipes. You will then also need suitable sealing rings (roll or lip seals, don't ask me which one is the right one). Your problem, however, will be that you then have the drain in the middle of the room and not on the wall. It would be sensible to break up the floor and then make the connection in the ground and lay it to the wall where the pre-wall element will then be placed. Is the black pipe in the corner a soil pipe from a bathroom above? Then you could also connect directly there and would not need to reroute the old supply line. With a vent pipe, of course, this only works to a limited extent, you would have to know the old pipe routing in the ground. If the whole bathroom is being renovated anyway and every cm counts: Take everything out, including the screed, and completely renew the wastewater pipes under the bathroom.

We also had an old cast pipe, which was removed by the plumbing company. They said it has to go if you're working on it anyway. I would also advise you the same - such pipes are not expensive, and once tiles are back on top, you won’t be able to get to it anymore. Better to do it right away!