Build over agreement for a manhole

20 Jan 2008
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United Kingdom
we are currently having our extension built and discovered a sewer pipe running that serves every 4 properties in our bungalow estate. Thames water have sent a letter to let us know that we will need a build over agreement as there is a manhole that will need to be moved. When we bought the house 4 years ago it had a conservatory at the rear and we have planning permission to knock down the conservatory and built a solid structure. Upon lifting the manhole there is a straight pipe that runs at the rear of our property and there is a pipe that comes from our properly and joins it, more like a Y shape.

They have told us that we need to make a new manhole 1 metre deep and run a pipe to the existing sewer and connect it with a Y pipe and then we need to to something they call a grubbing up process to seal the existing manhole so it is no longer in use. WE don't really have any idea how tho works, spoken to the builder and he said he was just going to leave the existing manhole and put a double seal cover on it and run a pipe to a new sewer to access it in the future. I told him it has to be done properly as thames water said that they will come down to inspect it as i have to apply for a retrospective build over as most of the wall are up and roof too and didn't know anything about this build over until this letter popped through.

Any help on what they want us to actually do and process involved and what do they mean by sewer needs to be grubbed up. I have attached a pic below to show whats under the existing manhole.
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Sorry i'm quite new to knowledge about sewers so might sound a bit dumb by asking what do you mean by removed? So what would happened to the straight pipe running as seen in the pic and what would happen to the pipe coming in on a 45 degree angle from my property? And how would they remove it?
If I follow your thread the main pipe we are looking at is to remain, as its the shared sewer, correct?

The one that joins it is going to be redundant correct?

The manhole is going to be redundant, correct?
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Yes the main pipe is to remain as that is where it will flow from my neighbour to neighbour. The current manhole has to be made redundant as you said and the one that joins it is the main waste pipe that comes from my property into it where all the waste flows out from to the main pipe so don't see how this will have to be made redundant?

The only way i can understand this from what they have said is we need to make a new manhole and the old one we will have to make mother y junction and have like a rodding eye access? Finally need to cover that open sewer pipe and then seal the manhole? Is that right? please correct me if i'm wrong as i said don't know much about this at all.
They are asking you to fit a new manhole outside of your extension, then run a new main waste pipe from your property to the new manhole, where you can get access for rodding etc. Then remove your old waste pipe, and fit a pipe in place of the old manhole and remove the manhole.
I kind of get what you have explained now, but not entirely clear, Ok so will make a new manhole as per thames water specs which should be about 1m deep and certain dimension made with bricks etc, We will then run a pipe from this new manhole to our existing manhole and connect this to that through a Y junction. So are we leaving the Old pipe that connects to the existing manhole as it is as the waste has to run from that old pipe which connect to all gutters in the property.

So what do you mean remove the old waste pipe? not quite sure about that, sorry to be a pain. I have drawn a rough sketch and is this what you mean? please correct me if i'm wrong.
Thank you very much for taking time out to make that drawing for me, makes more sense now when you mean replace open pipe, so thats the open pipe in the manhole that runs straight with a close pipe.
However the layout cannot be as you have drawn as new manhole cannot go by side of property has we have both neighbours who have their extensions there, hence i drew it as putting the new manhole further out in out garden rather then taking it towards the neighbours.

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