Interpreting sewer plan - likelihood of build over consent?

[BeachyDaz]

Hi all,
My colleague recommended this site as being a good source of help, so here goes!

We're at the point of exchanging contracts on a house which we plan to extend.

However the drainage search has shown that a public sewer runs up the drive, under the car port and through the back garden. This means it is approximately where we are planning on building the extension and parallel to the intended new exterior wall.

I've done my research on Southern Water's www and read a few other threads on various forums and most seem to agree one of the most important factors in whether we will get consent to build over or redirect the sewer is if the diameter of the sewer is <225mm.

Southern's site says that their plans identify the size of the pipes, but there are no sizes on the plan, just a key identifying that it is a "Foul sewer" (not a "Foul Rising Main" or "Foul Trunk" etc) with a "Dummy/S.24 Manhole" in the back garden and the same again in the road out the front.

So, my questions are:
Does this tell me what diameter the pipe is, or do I need to phone Southern to ask for more detail based on the manhole numbers?
and:
Is there likely to be further connection from the other houses on this road which further complicates this?

I've attached a screenshot of the bit of plan I'm trying to interpret below.

At the house, we can see the manhole cover in the road (8701) but there is no sign of the one in the back garden (8702), so we can't check the exact position without further specific drainage surveying etc.

 

[Hugh Jaleak]

Without seeing more of the plans, and ascertaining where that sewer goes to/from, it's impossible to gauge the size, but looking at it, I doubt it's a small one. The Water Company should be able to give you more info, alternatively if you can get someone to lift the cover in the road, then looking down the manhole should give you a rough idea of size.

However, instinct tells me, from that picture alone, it is likely to be a bigger sewer, as there's no small stuff to the individual houses marked.

 

[BeachyDaz]

Hmmm, that's what I thought (altho I have no prior experience of this, so thank you for your reply).

We clearly need to do a bit more investigation before exchanging contracts so I'll phone Southern Water first thing Monday.

 

[^woody^]

You need to either contact the water company and speak with the admin person or the local engineer about the pipe size. I'd agree with HJ that this could be a big pipe.

You also need to confirm the water company's policy relating to building over large pipes. Some allow it, some don't. And if this affects your plans for the house, then you need to think about it before you exchange.