Unusual Failure of WC Soil Pipe

[Simon M]

A flexible soil pipe fitted behind a WC has suddenly developed unusual holes in it which looks like its caused by rats but that seems impossible as its in a closed compartment.

See pic link;

I've thought maybe rats were inside the soil pipe but they would have to live inside and climb (or not get flushed down!) a later vertical soil pipe. After this joint the soil pipe is horizontal for a yard then goes into a vertical stack into the underground clay drain and away into the sewage pipes. The joint was first fitted in 2018 and must have failed suddenly over a few days because the water on the floor is new and obvious.

Several holes have appeared between the spiral steel coil reinforcement on the plastic. The plastic is not just split but missing material. The plastic was probably tight when fitted (due to the 90 deg angle) which could, over time, cause a split but not loss of material. Possibly its gone brittle and was a cheap Screwfix part.

I'll replace it with a proper elbow but am concerned what the cause is.

Any theories or previous similar experiances?

Thanks as ever for your help.

Simon

[Alan Lee]

Easy, cheap s**te plastic that has been exposed to cleaning chemicals, so has eroded over time.Add in the force of the water each time it flushes, and it just broke down. Just like plastic exposure to UV, it looks ok, but finally fails as it is so brittle.

[The Natural Philosopher]

Is that legal/advisable for soil pipes? Only ever used that for air...

[Andy Burns]

Certainly not advisable. Some pan connectors have a flexible section to "ease" alignment issues, I suppose they're justifiable if it avoids major re-work.

But for a tricky near-right-angle bend in a 110mm pipe run, you should use

[alan_m]

Constant use of bleach making the plastic brittle?

Either Screwfix or Toolstation used to do a cheap no-name flexi toilet waste pipe at around a third of the price of the branded version. Most reviews were rather negative with the main complaint that the flexi section was too thin and holes appeared within a year.

[Jeff Layman]

If it was caused by chemicals, surely you'd expect most damage at the bottom of the pipe where it would be exposed for more time than the top. Short of pouring certain organic solvents down the pan, PVC is pretty inert to most commonly used chemicals:

My guess would be mice, who can get through the smallest access hole. Rats and mice seem to enjoy a bit of PVC. Electric cables are a favourite.

[alan_m]

Depending where the bend is required, perhaps

[Andy Burns]

Looking at it again, it does seem more like a re-purposed tumble dryer vent hose :-P

[The Natural Philosopher]

I've used it on embedded extractor fans, too

[Adam Funk]

It's been a long time since I took chemistry, but I'm surprised by these:

Acetic Acid Not Recommended Acetic Acid 20% Not Recommended Acetic Acid 80% Fair Acetic Acid, Glacial Not Recommended

Why is 80% better than 20% or nearly pure?

There's "no information" for butter, coffee, or whey --- someone's not asking the real questions.

[Tricky Dicky]

+1 . I have a McAlpine flexible connector and it does not have a spiral of wire running through it. It is just a plastic concertina.

[Jeff Layman]

It seemed strange to me when I saw it. That info is repeated at other websites, but where the original came from I don't know. It is more sensible at

:Acetic acid, vapor R R* Acetic acid, 25% R R Acetic acid, 60% R N Acetic acid, 85% R N Acetic acid, glacial R N (*First R or N is resistance or not at 23°C; second is for 60°C )

[Adam Funk]

That makes more sense.

(I see that it also covers coffee but not butter.)