We have a problem with the cellar flooding intermittently. I know the cause, and I am seeking some advice about what we can do about it. Firstly I’ll describe the situation.
The house is Victorian, detached and contains 4 flats. All the foul pipes from the flats route into the cellar where there is an inspection chamber, and from there the pipe goes out under the front of the house towards the street. There is an unsealed cast iron cover over the chamber in the concrete cellar floor. The problem is that every 3 or 4 years the pipe leading from the chamber out to the main sewer backs up, causing the cellar to flood via the loose inspection cover. If we spot it quickly there might only be inch or so of water, but one time it wasn’t noticed for a few days and we ended up with about a foot deep of dirty water. It’s not a disaster, as the cellar is used for storage and we have learnt not to put anything that might be damaged directly on the floor, but clearing up afterwards is unpleasant to say the least and I would like to stop it happening.
The obvious first question would be to ask why the pipe gets blocked. I was told by one of the drain clearance operators who came to jet it out once that the pipe is of unusually small diameter and it’s probably unavoidable. I don’t know the diameter, but if he’s correct then clearly one option would be to excavate and lay a new pipe of the proper size. However, I suspect this would cost many thousands and I think we would take the view that it’s much cheaper to get it jetted out every once in a while, even if it does flood.
I have read about double sealed inspection covers, and it seems to me this should be a way of stopping the cellar flooding. It should also stop the musty damp smell that is usually present in the cellar. However, I have a major doubt about fitting one; if we did so, wouldn’t it just move the problem so that the first warning of blockage would be the ground floor flat flooding (not my flat, but still...)? If somewhere's going to flood, it's far better if it's the cellar. I suppose what I am asking is, is there a way we could get a prompt warning of the blockage occurring so that someone can call the drain clearance contractors before there’s any flooding anywhere? Is it legal to fit some kind of overflow pipe, or something like that?
Cellar flooding
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84-1093879891
Mmmmm...I can think of one simple way to create a 'containment and alarm' system, but just how feasible it is depends on the exact layout of your system and the cellar.
Anyway, the gist of it is to raise the level of the existing IC cover, by building up with 225mm brickwork, giving, say, 1200mm of extra height to the chamber. Top this with a sealed cover, to protect the property from smells and gases, and have a float switch fitted at, say, +750mm, so that if/when the effluent starts to back up, then it will trip the float switch some time before it reaches a critical level, and you can take some action, hopefully, to minimise the risks.
An emergency overflow would be great, if you had somewhere to overflow to, but, other than the floor of the cellar, there doesn't seem to be anywhere else.
It's worth getting a drainage contractor to price a re-construction of the existing narrow drain - it might not be as scarey as you think, and at least you'd know what sort of money was involved rather than guessing.
Personally, I'd always recommend a permanent solution rather than a stop-gap, but, if that's not possible, then the 'early warning system' described above might be your best option.
Anyway, the gist of it is to raise the level of the existing IC cover, by building up with 225mm brickwork, giving, say, 1200mm of extra height to the chamber. Top this with a sealed cover, to protect the property from smells and gases, and have a float switch fitted at, say, +750mm, so that if/when the effluent starts to back up, then it will trip the float switch some time before it reaches a critical level, and you can take some action, hopefully, to minimise the risks.
An emergency overflow would be great, if you had somewhere to overflow to, but, other than the floor of the cellar, there doesn't seem to be anywhere else.
It's worth getting a drainage contractor to price a re-construction of the existing narrow drain - it might not be as scarey as you think, and at least you'd know what sort of money was involved rather than guessing.
Personally, I'd always recommend a permanent solution rather than a stop-gap, but, if that's not possible, then the 'early warning system' described above might be your best option.
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67-1093879108
Tony, thanks for your ideas. Your "containment and alarm system" would be feasible, though not necessarily the most convenient. But I like the idea of an overflow, because it would a low-tech, passively reliable solution. It should in fact be possible because the cellar ceiling is slightly above ground level and an overflow pipe could discharge out of the front of the house. The effluent would run across the forecourt, across the pavement and into the gutter. I'm slightly suprised this would be permissible - even if it wasn't discharging, it would be an open vent to the foul system at ground level. But if it is allowed, which you seem to imply, what would be the best way of doing it? It strikes me the cheapest and easiest way would be to put a T piece at the bottom of one of the soil stacks before it disappears into the cellar floor (about 1.5m below ground level) and then run a pipe up to ground level out of the front wall. Would that be OK?
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84-1093879891
There seems to be a misunderstanding - you cannot discharge sewage into an open environment. Any overflow system you install mustdivert the sewage effluent to another sewer, not to the open air, not to run across a pavement. This is why I stated that an overflow system is fine as long as you have somewhere for it to overflow to, ie, an alternative, unblocked sewer. The only alternative is to flood the cellar floor, which is what currently happens, if I understand your first post correctly.
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67-1093879108