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Q&As
Is Our Extension Over a Drainage Pipe Acceptable?
Hello, I have googled relentlessly but can't seem to find the answer, I hope you can help.
We are in the process of planning a renovation. Part of the works is an extension across the rear of the house to replace an existing conservatory. The conservatory is about 6.5m wide and is built over an Anglian water sewer drainage pipe. The foul pipe services the houses further up and down the road but our sewage actually enters it after it passes out of the side of our house (boundary) and into next doors garden, so we do not have a man hole in our garden for this pipe.
As part of the works, we want to build a man hole on one side of the conservatory to tap into this pipe to connect new services on that side of the house (current sewer services on the other side) thus giving us an inspection/maintenance point in the process.
This is not in itself a problem. The problem is that Anglian water state a build over a drainage pipe cannot exceed 6m. The new extension would be just over the 6.5m length of the conservatory that is already there. So if the existing build over exceeds the 6m length and we are just 'replacing it' and assuming improving it, would this be acceptable?
We would want to add another inspection man hole the other side too, effectively adding inspection points either side of the extension that are not already there. Currently the length between man holes (in neighbours gardens either side) exceeds 14m, so we would be adding two incremental man holes in that length.
We have had a drain survey so we know the location, condition etc... The guy doing this said he has seen domestic build overs well in excess of 6m without man holes and said he didn't see an issue. Our architect on the other hand thinks a re-route may be needed.
We would appreciate your advice and opinion.
Thanks
Steve and Sarah
One Answer
Whenever you are building within 3m of a public sewer, it is usual that you will need to enter and negotiate a Build Over Agreement with the water authority who are responsible for the maintenance of these drains. It is also a requirement of Building Regulations (part H4) that this has been undertaken when they are also checking your proposals.
The water authority will want you to firstly consider proposals that would avoid the sewer or divert the sewer as this will make it easier for them to maintain it. However, in your case there is already an extension built over the sewer which could have become public after the extension was built; as the rules of water authority responsibility changed in 2011.
You need to first assess what type of drain this is – the thinner the pipe approx. 160mm diameter or less the easier this will be to deal with. I would suggest that you submit your application to the water authority and start to liaise directly with them about your choices.
I agree with you that you intend to make the current situation a lot better in terms of future maintenance and this should be considered positively. In addition to the manholes you are suggesting either side of your extension; you could also consider introducing an external manhole or rodding point half-way through the 6.5m run enabling an effective way to get rid of any possible blockage.
Once you start this process and put across the “improvements” hopefully the water authority will enter into positive dialogue with you so you find the right solution. Ensure you do this well in advance of starting on site as they may not be the quickest authority to deal with.
– Opinder Liddar, Build It Expert