Odd drain

[CliffordPope]

I have just uncovered this drain when digging out an unwanted plant, which I found was growing in the drain

The vertical stack pipe comes from the upstairs loo, and the junction on the left takes waste on down to the cess pit. The plant was the only thing stopping waste from bubbling back into the border - when I dug it out and tried flushing the loo water welled up backwards out of the drain.

I have now removed the superfluous drain and blocked off that limb of the pipe connector, but what can it ever have been for?

 

[Lime]

Well, the obvious answer is another sink/bath/drain pipe used to feed into it.
Perhaps the upstairs bathroom sink/bidet/shower/bath wastes now feed into the stack pipe.
I'd be more concerned that there is backflow/backup in the pipe going to the cess pit.
The pipe into the cess pit should be a relatively free-flowing pipe.

 

[CliffordPope]

There's no evidence that anything else ever connected to it. It's not obvious in the photo, but it has a square section to take a small metal grid, about 3 1/2 " .
The reason the waste flows back up it is that it is slightly lower than the pipe to the cess pit, so water etc can flow backwards round the U-bend.

 

[MikeG]

I can't see your photo as anything other than a tiny thumbnail, so I'm just guessing. But if there was a square grate on the top then it was likely at the termination of a downpipe, taking rainwater from the roof into the foul drains........which isn't a good plan.

 

[MikeG]

Sorry, had to run off and do something else........

The other thing it could be is a gully/ trap from a waste pipe from a sink or handbasin.

 

[88v8]

... taking rainwater from the roof into the foul drains........which isn't a good plan.

No, but it was pretty customary, and on an old house I wouldn't bother to unpick the arrangement.

Ivor

 

[Flyfisher]

Doesn't it depends on the foul drainage for the property? An old house may have a septic tank and, depending on its capacity and condition, connecting surface water drainage as well could overwhelm it in some conditions, which might not be pleasant. If connected to a mains sewer then the addition of surface water drainage should do no harm in most circumstances, though it wouldn't be standard practice these days. I also believe that mains sewerage charges are higher if surface water is sent to the foul drains rather than a soakaway.

 

[Lime]

There's no evidence that anything else ever connected to it. It's not obvious in the photo, but it has a square section to take a small metal grid, about 3 1/2 " .
The reason the waste flows back up it is that it is slightly lower than the pipe to the cess pit, so water etc can flow backwards round the U-bend.

(The photo is quite clear if the browser zoom lever is increased to 400%.)
The additional pipework you refer to is typical of a clay gulley with trap and square top (usually with a metal grating) for taking the discharge from sinks etc.
It is quite possible that the stack pipe did not have the WC connected to it originally and that the clay pipes in the ground pre-date what is visible above ground.
In that case the stack pipe would have acted as a vent pipe to the cess pit or septic tank.
When the bathroom and WC were installed, back in the day, it was standard procedure to run the WC into a 4" pipe separate from any other bathroom discharge.
Sinks, showers and baths would probably be discharged into a hopper then into a down pipe and empty into the square drain you have removed.
It is only very recent (after the war) that sinks and baths have been allowed to be discharged into the same pipe as the WC.

It is also clear that the square opening is higher than the clay junction in the cess pit pipe.
I'd expect some backwash into the other branch of the junction but not over and above the square top of the old gulley you have removed.
For it to overflow means either there is an obstruction below the junction preventing the discharge from the WC flowing directly into the cess pit or the cess pit is full.

 

[CliffordPope]

Interesting explanations.
Yes, I think probably the stack pipe was not originally connected to a WC, as I don't think there was one indoors, only in a brick extension round on another wall.
Both it and the drain in question connect a few yards further down the pipe and run into the cess pit. So it does seem unlikely the the grid was meant for rain water, partly because as has been said it would be silly putting so much water into the cess pit, but also as the roof gutters drain elsewhere and pass down an old clay pipe into a stream running down the side of the road. Perhaps there was another outbuilding/washroom with a grid for a sink. I've checked the levels and suspect that the clay pipes had sunk, putting the grid at a slightly lower level than its outlet.

I assume there must be a cess pit somewhere - the pipe just disappears into the ground, and there is no trace of any covers or exit. What actually happens I don't know - There is a good flow down the pipe, no backing up, no sign of any wetness welling up anywhere. The garden slopes away from the house, and I appear to have simply a never-filling hole. It has not been pumped out or attended to in 50 years, probably never. The rock below the subsoil is rather crumbly shale, the strata lying upright on edge, so draining well.

 

[Pennyviz]

ha - all my storm water gutters discharged into the soil pipes and thence into cess pit which overflowed into the stream at bottom of garden ..... Having said that the old privy also went directly into the stream so possibly was an improvement!