On Tuesday, 6 November 2018 09:34:00 UTC, Chris French wrote:
Hi folks.

Ok, downstairs toilet is a S trap pan cemented into a clay pipe
sticking out of the floor. Low level WC, not close coupled. A
measurement of the end of the pan trap is about 110 mm. So and
old size pan with a slightly larger size outlet than modern ones
it seems.

The pan has cracked on the exit part of the trap such that it
leaks, so it needs replacing.

My main concern is not breaking the clay pipe :-)

Any experience /suggestions on the best approach?

Options seem to be to use a new S trap pan and cement it in after
removing the old cement. Though presumably as the old pan outlet
is larger, if I could just remove the old pan outlet remains from
the cement it could fit the new one in and then seal around
it?

Or use a horizontal outlet pan and a suitable pan connector.
Either into the cement ring or down into the pipe, which would
seem a better idea.

Any comments?



Use a horizontal outlet
--
Chris French

You'll probably find that the cement in the socket is not solid.
The practice was to put ropelike substance called "Gaskin" in the annular slot first & then cement on top. This centralised the pipe and stopped cement falling into the drain.
Best removed with angle grinder with diamond disk.
You may have to smash the WC to bits.
On the other hand, you may find it "wiggles", the cement has not adhered to it.