Drain blocking

stuart45

The main problem with combined systems is the overloading of the system so it means a discharge into the river is more likely. It's quite common to have a 6 inch pipe running along the back to take a number of houses. An extra extension shouldn't be an issue.

Yorkie1

Well the drainage people have been and successfully done their bit. It looked as though it was just a build up of dirt. I watched the water as it was jetted down the pipe, and it was just black. No lumps, obvious fatbergs, wet wipes etc.

The output from the gully and the soil stack combine under the ground, to feed into the shared pipe at the manhole cover. (Not sure about where the runoff from the rainwater downpipe goes to, and didn't think to ask).

He put a camera down the pipe from the gully. No obvious evidence of broken pipe; there was a slight displacement at one point, but he said it wouldn't have been sufficient to cause the issue. He asked if there was a cover for the gully (there is a plastic one to stop leaves getting down it), but I think I'll move the pots away from very close to it.

Thanks everyone for your comments. At least it wasn't to do with the neighbour's builder!

stuart45

Glad it's sorted. The pipe that runs along the back of the houses looks like a 6 inch pipe, so should be enough to handle any extra rainwater loads.

WIAWSNB

Good result, Yorkie.

Could I ask - who were the 'drainage people'? And when that inspection cover was first lifted, what was the water level inside like?

Yorkie1

https://forums.moneysavingexpert.com/discussion/comment/82014534#Comment_82014534

They were a local plumbers' firm in N Yorkshire who have a business drainage firm within their offer.

There was no water in the pipe when the cover was first lifted. Just a trace in the side pipe from the house.

The dirt in the pipe was probably from the surrounding of the manhole cover, which fell in when it was removed, I think (rather than in there and dried out).

Section62

https://forums.moneysavingexpert.com/discussion/comment/82014748#Comment_82014748

The chamber is fairly clean, and there is no 'tidemark' to suggest there has been water standing in the chamber due to a downstream blockage. As the water seemed to be around the gulley grate level this chamber should have been nearly full.

My bet would normally be on the gulley being trapped and the trap getting blocked by 'stuff'. Is that a possibility?

I agree with stuart45 that the main run looks like 6", and therefore unlikely to be troubled by some extra runoff from extension roof drainage.

Yorkie1

The chap said that the blockage was very close to the gulley. Could you clarify what you mean by it being 'trapped', please? Do you mean like a U-bend under a sink?

WIAWSNB

As S62 suggests, this doesn't really add up.

There was no raised volume of water under the cover - it was free-flowing - so there was no blockage, unless there's a partial one further down the pipe that happened to have slowly drained away before the guys turned up. And they did a CCTV from the gully - as in your photo - and all is clear. So, what is the issue?!

Your pic of your gully grate shows the water level as being a few inches below it, which is what you'd expect - the gully is a U-bend, like the trap under your kitchen sink, and is designed to hold water at this level to create a seal against smells.

So, this is weird.

As you continue to use your kitchen plumbing, have regular ganders at the water level under the grate, and see if it stays around the same level - it should. If it rises significantly, or comes above the grate, or threatens to overflow, then you really need to lift the inspection chamber cover pdq and see what the heck is going on. If the water level under there is also high, then there is a blockage further down, and it isn't your issue to sort - it's the WB's. Take a photo of this right away. The 'normal' water level in there will be surprisingly low - for showering, dishes, washing machine, etc, you'll get a half-inch depth of water flowing smoothly past. Obvs with a 'flush', it'll briefly be a little more dramatic, but still well below the pipe cut-out - just an inch or so's depth. With lumps.

As it stands, it looks as tho' you have paid I presume well over £100 to find out precisely now't - it remains a mystery. 😶

Do you have the required lifting whatsits for the cover?

Yorkie1

Re. the trap / U-bend, thanks for the explanation. Will keep an eye on what's going on over the next few days. The level of standing water in the gulley is definitely quite a bit lower now than it was beforehand.

The plumber removed the gulley and put a hose down it. When I asked him where the blockage had been, he said it was very close to the gulley, where I've indicated a guessed cross below. (I suppose it could rather have been in the U-bend, perhaps).

The CCTV was done after the drain blockage had been cleared, so I would expect it to not show anything.

A very (!) rough sketch is attached below. I don't know the exact route for the gulley (bathroom, sink, dishwasher, w/machine discharge) drain and soil stack drain to merge, but it happens underneath the concrete between the house and the main shared drain. I don't know whether the rainwater drainpipe runs into the shared drain separately, hence route not shown.

May need to get some devices to lift the manhole cover. He used two angled screwdriver type implements under one corner.

WIAWSNB

https://forums.moneysavingexpert.com/discussion/comment/82015009#Comment_82015009

Ah, ok that now makes sense 🙂

With no cover over the grate, dust and dirt will end up in the gully, and also moss/tile grit from the roof, and this can (will) build up at the bottom, thereby restricting flow. If the dirt that was shifted by his jetwashing was there, then it all fits in.

In which case, mystery solved - and it was your issue to resolve.

Yes, worth getting a nicely-fitting cover to go over the grate to prevent stuff getting blown or washed in there.

If the wee grate lifts off, you can stick yer marigolded hand in there every year and scoop out the collected debris - that should sort it.

And no need to lift the inspection chamber cover to check, as now't will be there. 😉