Clay/cement toilet collar leaking

Hi,

My mother's toilet has started leaking onto the floor when flushed from the clay or cement 'collar' that joins the toilet to the waste pipe. It doesn't happen every single flush, but when it does you can see the water coming out of cracks in this collar and it makes a decent pool on the floor.

Is it possible for me to apply silicone, or some kind of putty, to the cracks or does it need to be replaced entirely by a plumber?

Given that the toilet itself is stable, what would have caused this collar to break down?

This is a 50's era house, and the toilet itself was last replaced about 32 years ago.

Thanks

It depends if the crack is in the collar itself or the leak is only at the join. If its the joint then you can use silicone, they type you can apply to a wet surface is the best.
If there's a crack in the collar and you can see the entire crack you may also get away wth silicone.

What causes it' building movement due to building heating cooling, slow chemical reaction, change in diet, medication, . . . . .

Thanks for that.

I opened the inspection point upstream and their is a visible partial blockage. I wonder if that caused some kind of back pressure when the toilet was flushed, damaging the collar?

I think I'll get a plumber to snake everything and replace the collar. Don't much fancy ferreting around in sh*t :)

Yes, a partial blockage can cause the symptoms you describe. I would try a silicone fix and blockage clearance as to actually replace the collar would involve removing the pan which is often cemented down so gets damaged when removed. In other words, replace collar, replace pan, you might as well replace cistern as well, then there will possibly be floor repairs and wall repairs = $$.