Manhole

[ChrisKingston]

I had my food dye ready to try to figure out what was going on with drains in my new house, lifted the manhole cover and found this...

There are pipes at each end that look a bit like clay underground drains, and are at right-angles to the road (where main drain probably goes).

I flushed a loo three times in a row and a little bit of water came in at the end nearest, but only a bit. This manhole is about 6ft from the house wall, although quite a bit further from the loo I flushed (at other side of house).

Is this just a very clogged up inspection chamber for a main drain? Or is it a soakaway of some kind? Should I dig it out?

I'm a bit stumped.

 

[John D v2.0]

Looks more like someone had the task of disposing of some unneeded concrete and found a convenient hole to throw it in?!
Or it could just be rodding access in substitute for a chamber that's been removed due to an extension
Perhaps there are other inspection covers you can lift, maybe this is the upstream chamber?

 

[ChrisKingston]

Looks more like someone had the task of disposing of some unneeded concrete and found a convenient hole to throw it in?!
Or it could just be rodding access in substitute for a chamber that's been removed due to an extension
Perhaps there are other inspection covers you can lift, maybe this is the upstream chamber?

Thanks, yes I hadn't thought of that!

House hasn't been extended properly and haven't found any more inspection covers yet - although might lift a few bits of decking to check.

 

[Nige F]

Easy to see if it's concrete - poke it with a stick

 

[ChrisKingston]

Easy to see if it's concrete - poke it with a stick

Yes I gave it a poke. Not concrete. Sludgy and didn't smell of poo, although the house was empty for almost two years.

 

[Hugh Jaleak]

I'd hazard a guess you've got an Interceptor there, on the outlet side of that chamber. It's blocked, allowed waste to build up as seen, with the water escaping via the rodding eye, top left of chamber. Hence why you saw a trickle of water coming in when you flushed the Loo.

Suggest you try not to stir it up more than you need to, (risk of Hydrogen Sulfide gas), if you can get the outlet clear, (under the rodding eye), then throw in copious amounts of water to break it up and wash it away.

 

[ChrisKingston]

Thanks Hugh I've done some googling and that makes a lot of sense. So there is another inlet under the larger hole to the left of the picture above? There was also a strange pipe out right up by ground level with a pot over it in the garden - which would make sense for gas release. I'll get some more pictures tomorrow.

Do you get interceptors for combined sewage/surface water drains?

Can't I just jump down there and dig it out with a trowel or small spade into rubble sacks? What if I wore a mask? I think it'd take forever to try to break it up with a hose.

Having spoken to a neighbour there might be another manhole under some decking that I haven't pulled up yet.

 

[Nige F]

Do you get interceptors for combined sewage/surface water drains?

Can't I just jump down there and dig it out

Yes to combined - NO dont' jump down ( unless you've got waders) - you'd break your ankle on the sloping benching and channel @ the bottom. A local hire co may have a gully scoop or grab

 

[Hugh Jaleak]

+1 for Nige's advice, do NOT jump in, you dont know what is down there, or what you're stepping on/in. Scooping it out, well you'd need a very strong stomach, that's going to be very well decomposed, which as I mentioned previously, creates Toxic gas, a mask wont help with that, the Professionals have to use BA Kit when entering any areas where there is a risk of H2S.

If you can get the outlet clear, you'll soon crack it. Although there may look a lot, it's surprising how quickly it breaks up and washes away. Not sure where you are in London, Andy from Herts P&D (Plumbing and Drainage) covers the North London area, he'll soon sort that for you.

 

[bernardgreen]

+1 for Nige's advice, do NOT jump in,

+2 for not getting into the chamber

Getting in is relatively easy, getting out can be more difficult.

 

[HERTS P&D]

I come accros lots of these manholes like this, I always flush it with gallons of water and just rod the outlet. The more water that is applied, the liquid it would become.

Andy

 

[ChrisKingston]

+1 for Nige's advice, do NOT jump in, you dont know what is down there, or what you're stepping on/in. Scooping it out, well you'd need a very strong stomach, that's going to be very well decomposed, which as I mentioned previously, creates Toxic gas, a mask wont help with that, the Professionals have to use BA Kit when entering any areas where there is a risk of H2S.

If you can get the outlet clear, you'll soon crack it. Although there may look a lot, it's surprising how quickly it breaks up and washes away. Not sure where you are in London, Andy from Herts P&D (Plumbing and Drainage) covers the North London area, he'll soon sort that for you.

If I just blast it with the garden hose would that be enough?

I won't jump down there then, thanks!

Unfortunately I'm south west London (Kingston area) so think it might be too far for Andy in Herts. Think will get a pro in to look in the new year though!

 

[Hugh Jaleak]

Depends whats in the trap, they often fill with compacted grit and silt, so need a bit of effort to break it up and get the water flowing. Might be able to achieve something with the corkscrew attachment on some drain roads, finishing off with he plunger to push the remainder through, otherwise, it'll need High Pressure water jetting, a job for the pro's.

If getting someone in, avoid the Franchises, and get a fixed price to do the job. it's a blocked interceptor, not a difficult job usually.

 

[ChrisKingston]

Gave it a good blast with a garden hose then rodded it too, and have got it pretty clear.

Thanks very much Hugh you were spot on - it's an interceptor - and the ceramic lid had fallen off and down into the main gully (though thankfully it hadn't broken). Will maybe see if I can get it taken out if I get someone to help me make a fresh connection to the drain.

 

[Hugh Jaleak]

They can be smashed out and a section of pipe fitted in place, if you really want rid of it, but there are still plenty of them up and down the country, just keep an eye on it, and any signs of the trap filling with detritus, give it a good clean out and it'll be fine for a bit longer.