Sewerage Drains.

19 Aug 2007
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West Midlands
United Kingdom
I have a query, Not sure of the best way to describe it, but here goes, we had a modular building installed on a plot of land, the waste systems,ie toilet, sink etc were connected by the builders to the drain, this was about three months ago, the drains blocked back to the toilet, I fetched up the manhole covers to find total blockage, I rodded and cleared right back to the edge of the property, once cleared I found that the drain run inside the manhole nearest the road was at different levels(highest going out) which I found strange, on calling back the builders they tell me that this is some kind of grease/silt trap, I have never seen this in a sewage drain before, can anyone advise if this is correct, could this be a rainwater drain run??, your advice is welcome. Thanks...
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I suspect they're telling you porkies. Drains work on gravity, how old is the drain connection into the road? You may have found what is known as an 'Interceptor', and the higher pipe you can see is the rodding eye. The outlet for the water is below that, these often block and so wont be visible under the water/waste. Have a poke in the bottom with your rods, should be able to 'feel' the outlet. Couple of good stabs with a plunger may clear it.
I would say that the drainage run is quite old, when I say that the out going pipe is higher, I mean only by approx. 2 inches, I can see the bottom of the chamber and its the open channel part of the drain is lower, just a note to say that this site is a commercial site, we are the only property on this drainage run, there are four inspection chambers that are in pairs along the drive...
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Pretty certain it's not a grease trap, so discount that one! The channel will drop sharply into the 'U' bend of an interceptor, and if the drains are pre 1950ish then there's a good chance there'll be an interceptor fitted. Photo of bottom of chamber would help if poss.

Chambers in pairs could indicate storm and foul sewers running in parallel, just make sure when your builders connected up, they connected to the foul and not the storm......

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