Blocked pipe outside, what is this?

Recently got renovation work done and was checking outside drainage when I noticed one of the down pipes didn't appear to be draining well.

This info isn't 100% as these pipes are buried and where they actually go might be different to where it looks like they should go; but there's a good chance this down pipe's drain should connect with a junction of drains a couple of feet away. I noticed water wasn't running into that junction so I felt in the pipe with my hand and it felt blocked.

I took a photo and it looks like the pipe is jammed with a perfectly sized lump of granite. So the causes as I see them are these:

1) Somehow a lump of granite which almost perfectly fits into this pipe has ended up blocking it. Unlikely.
2) This rock has been crushed into the pipe from trucks etc. driving above.
3) It isn’t granite but rather some congealed building material, although chipping at it with a screwdriver it certainly feels like granite would.

So option 1 seems unlikely but option 2 would surely mean that there’ should be damage above the pipe (there isn’t any) and there should be visible evidence of shards of plastic where the pipe was crushed, there isn’t.

Fourth long shot option the rock was put there deliberately by the builder to stop excess water flow??! Sounds unrealistic.

Can anyone have a look at the attached photo and tell me what they think or if they’ve seen anything like it before?

Thanks.

Can't link directly due to my low post count so here's the url:

i.imgur.com/EbwtErg.jpg

I presume the photo is taken from within the Access Junction chamber looking along the horizontal pipe. We are not looking up or down? Correct?

It's hard to tell from a photo but could it be that that the Access Chamber is just not connected to any pipe and what you see is just builder's rubble/hardcore?

Is it the rain water down pipe that is connected to this and not the sewer stack?

Correct on both counts this is from the junction looking back towards the down pipe. So you're looking horizontal not vertically.

And yes it's the rainwater down pipe.

Assuming it isn't connected is this normal practice? Why have a junction and a pipe that goes nowhere?

There's also a gutter (one of those covered gutters that have a grille on top) that runs the length of the drive and the pipe at the end of that also appears to end near the junction but doesn't go into it!

One other point, this house has a septic tank so maybe there's some restriction on the amount of water than can be put into them? For instance in a heavy downpour if that pipe was connected it might send too much water? Guessing here.

Hi Michael, my understanding is run off water (fromm down pipes etc) goes into a soakaway and shouldn't go into your septic tank.

Looks like a cut out from a kitchen worktop. Did you try pulling it out. There seems to be space at the bottom where you could push in a bent steel rod and pull it free.

bstop said:

Looks like a cut out from a kitchen worktop. Did you try pulling it out. There seems to be space at the bottom where you could push in a bent steel rod and pull it free.

Click to expand...

The angle is such that even getting a screw driver in there is difficult. It's not smooth topped like a counter top would be and we've no granite counter tops anywhere in the house.

I wonder though, if the septic tank / rain water thing is correct (as in they shouldn't be connected) then maybe this was the builders attempt at letting the rain drain away. Surely though the distance the rain is piped to should be far enough from the house to avoid damp problems. Currently it's essentially draining about 6 inches from where it is gathered.