ᐅ Is it possible to branch off a toilet connection from an old cast iron pipe?

Hello community,

I want to renovate my very small bathroom and need to make use of every centimeter (inch).

Unfortunately, there are old pipes inside the wall. The toilet drain is also about 40 cm (16 inches) away from the wall. Is it possible to install a wall-hung toilet and connect the "new" drain directly to the cast iron pipe (see attachment)? The cast iron pipe (built in 1970) has a diameter of about 11 cm (4.3 inches).

Best regards,
Zwusel

In principle, this works quite well. Cut out a section, add a branch, and seal it with sleeves. I found a similar setup in my own home. It looks professionally done. However, you will probably get different answers here on how to do it correctly.

A wall-hung toilet also requires the wall with the cistern. This typically has a depth of just over 20cm (8 inches). Conveniently, the drain to the soil pipe is usually integrated in this. This approach seems very practical here, although I can’t really assess the statement "need every centimeter for this." There might also be (more expensive) shallower versions available, which is worth checking.

In principle, you can connect new HT pipes to old cast iron pipes.
The pipe, built in 1970, was previously called a GA or LNA pipe (now known as SML). You can get adapter fittings to connect these to the currently used HT pipes. You will also need suitable sealing rings (either rolling or lip seals—don’t ask me which one is the right choice).

Your problem will be that the drain will end up in the middle of the room instead of against the wall. It would be more practical to break open the floor and make the connection underground, then lay the pipe to the wall where the pre-wall installation system will be placed.

Is the black pipe in the corner a soil pipe from a bathroom above? Then you could connect directly there and avoid rerouting the old supply line. However, if it’s a vent pipe, this is only possible to a limited extent—you would need to know the old pipe routing underground.

If you are renovating the entire bathroom anyway and every centimeter counts: remove everything, including the screed, and completely renew the wastewater pipes under the bathroom.

We also had an old cast iron pipe that was removed by the plumbing company. They said it should be taken out once you are working on it. I would recommend the same to you – these pipes are not expensive, and once tiles are installed over them, you won’t be able to access them anymore. Better to deal with it right away!