Mysterious soil pipe blockage

Had to solve a drip from the (P-trap) toilet pan yesterday. Seal in plastic connector had hardend. Pulled the pan away from the pipe to have a solid lump of concretion fall into the floor. Worked the connector off the pan outlet to find even more concretion in the connector and foul water pipes. The U-bend is reduced to around 2 thirds of is actual diameter.
Now this toilet has never flushed waste away very well but I think we now know the reason why.
I've cleaned out what I can of the concretion, which looks like plaster. Toilet now flushes better.
Do wonder if the builders disposed of their plaster excesses down the toilet rather than taking it outside. Neighbour didn't have the same issue when they replaced their bathroom.

wgt52 said:

Do wonder if the builders disposed of their plaster excesses down the toilet rather than taking it outside.

Click to expand...

Some "builders" do dump left over waste down the toilet.

An update on this courtesy of my improvised cr*p cam (!)

That third dry inlet in the inspection chamber at the front of our house is definitely a pipe, not capped, and as you can see from the photo, there are marks on the pipe wall that suggest it has been used for it's purpose.

We've had no further back up of water in the en-suite, though we have continued to avoid using the en-suite toilet - and just stuck to using the power shower and sink in there.

Possibilities seem to be:

1. The en-suite is indeed connected to the third inlet of the front inspection chamber as you might expect it to be, but that pipe is well and truly blocked. That would mean the water we're currently putting down must be escaping out the pipe before the blockage. Problem I have with that theory is:

a) That suggests the pipe is also damaged allowing water out - but we have quite high clay content in our soil and I just don't buy the idea it could soak away the output from a power shower.
b) There is the fact that some sort of blockage did exist and has now evidently moved - and that will have been solid (!), so where did it go?

2. When I opened the storm drain cover, I was a little surprised to see the outlet from it was heading across the drive as shown below, rather than towards the road as I would have expected. This made me wonder whether the en-suite soil stack might have two outlets below ground. The lowest point where it curves to the horizontal and on to the inspection chamber and is well and truly blocked AND a second outlet higher up the stack but still below ground that perhaps goes to the surface water drainage system as a sort of overflow, and it was this which had also blocked and has now cleared. But unless the pros on here know any different, I've seen nothing that suggests this would be in any way normal.

3. That third inlet is a dead end further up the pipe, and the en-suite goes an entirely different route to the sewer with no rodding access. But the signs of past use make this option unlikely.


Unless anyone has any flashes of inspiration, I'm thinking this leaves me two choices now:

Get the pros in with drain mapping gear - and they will probably start by putting a camera up that third inlet and seeing what is on the end of it.

Cut a hole in the box section in the hall and put an inspection panel in. It seems that PolyPipe do like a retrofit rodding point (pic below) where you cut a hole in the soil stack and stick this saddle on with solvent weld. Anyone used one? That would certainly allow me to get my own USB camera down to take a look - and it also gives an easy route in for the pros (and for any future problems) if my own findings are inconclusive.

At this stage I would seriously try a dye test before doing any more. It may prove inconclusive, but you've nothing to lose by having a go.

Hugh Jaleak said:

At this stage I would seriously try a dye test before doing any more. It may prove inconclusive, but you've nothing to lose by having a go.

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Thanks for the advice. I'll give it a go - but the only thing I can be absolutely certain of right now, is that none of the water going down the soil pipe is turning up in any of the three inspection points I am able to access. Mrs Midge was repeatedly flushing the en-suite loo for me today whilst I was checking around, and nothing - not even a trickle.

Dye will be obvious, if it appears!

Finally got around to a bit more diagnosis on this. Thought I might as well open up the box section in the hall where the soil pipe is, cut a rodding point in and at least take a look myself before I admit defeat and call the pros in to do a mapping job.

Only a couple of things of note:

1. The slight mis-alignment of the pipes might just have been a factor in the original blockage we had, but it must have been like that since the house was built - and we've not had any problems in the 28 years we've lived here until now.

2. It looks like the pipe is heading slightly to the RIGHT away from the rodding point at the front of the house and its mysterious dry inlet. So all I can assume at this stage is it's a separate pipe all the way to the main sewer and no rodding point.

YorkshireMidge said:

... That would mean the water we're currently putting down must be escaping out the pipe before the blockage. Problem I have with that theory is:

a) That suggests the pipe is also damaged allowing water out - but we have quite high clay content in our soil and I just don't buy the idea it could soak away the output from a power shower...

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sadly the long-term leaking soil or waste pipe is not very rare. It will wash away the soil to form a hollow or cavity in the ground, enabling future leaks to be accomodated more easily.

Sometimes this becomes apparent when the ground or paving above settles and sinks into the hole; sometimes it becomes apparent when the house starts to subside.

I had a relative whose manhole beside the house was somehow blocked or broken by builders demolishing a greenhouse and putting up a garage. Around 50 years later the house wall subsided. By that time she was very old. I once lived in a terraced house where the soil pipe had been broken and leaking, probably since 1942*. I discovered it when laying a new patio. My neighbours on both sides had the same, but were not aware of it, until their bathwater bubbled up in the hole I was digging.

*the date is highly relevant.

JohnD said:

sadly the long-term leaking soil or waste pipe is not very rare. It will wash away the soil to form a hollow or cavity in the ground, enabling future leaks to be accomodated more easily.

Sometimes this becomes apparent when the ground or paving above settles and sinks into the hole; sometimes it becomes apparent when the house starts to subside.

I had a relative whose manhole beside the house was somehow blocked or broken by builders demolishing a greenhouse and putting up a garage. Around 50 years later the house wall subsided. By that time she was very old. I once lived in a terraced house where the soil pipe had been broken and leaking, probably since 1942*. I discovered it when laying a new patio. My neighbours on both sides had the same, but were not aware of it, until their bathwater bubbled up in the hole I was digging.

*the date is highly relevant.

Click to expand...

Agreed - whilst I think I know what is going on now, I still intend to get it mapped and checked.

Well, I'm glad I did have it checked. Got the pros in this morning and the dry inlet to the front rodding point has a completely collapsed and blocked pipe 3.6M in - which unfortunately is under our concrete hall floor close to where the soil pipe goes vertical. So there MUST be a cavity in the ground allowing any water that has gone down from the en-suite to soak away. So it's gonna be a fairly big bill and a lot of mess but at least the mystery is finally solved. Thanks for all the contributions.