Survey has shown public drain at rear of property

[Cosmos123]

Hi
A property search has shown public drain on the patio where we would have liked to built a rear extension.
Has anyone had experience of this.
Although I assume costly, could the public drain be moved further away with permission from the water company.
Thank you for reading.

Depending on the size of it, you may be able to build over it. Google your water company + build over consent.

There will be rules about how close the footings can be to the drain and the depth they have to be, and potentially manhole covers to be added.

*Public sewer pipe

Hi OP, this is pretty normal - it's a shared sewer that you and your neighbours' waste all flows into, right? We built over one with our extension last year. Both the building regs guys and the water company came out to inspect the foundations to check the builders had done it all to spec. We paid £300-500 ish (can't remember!) to the water company initially for the build-over certificate but no major hassle.

This is the map

The public sewer is the red square.

Thank you @WoolyMammoth55 and @NothingIsWrong for your replies.

Sounds reassuring

My old neighbour built over one with seemingly no issues.

If the brown line is the sewer line it would appear your neighbour has already built over it. The red square (manhole?) might need to have an internal manhole cover fitted inside the house so it is still accessible.

I would say you stand a reasonable chance of being allowed to build over but please please do get this sorted first, before you spend too much money on other professionals such as architect etc.

Yes the brown line is a sewer line.

Maybe we could move the manhole so it is not inside the property.

I prefer not to have access internally.

We moved into a house where the extension was 1m shorter than the extension next door because of a sewer access panel - but the extension was done in the 1990s - building regulations and techniques probably mean you have more options now!

Bigger map so you can see more properties.

OK, multiple properties have built over so I reckon your chances are not too bad. The sticking point is the manhole. Depending on the regulations for your water company, they may let you move it along the line of the sewer closer to your boundary with your non-attached neighbour so it's outside - assuming you are not building the full width of your land. Obviously you will have the cost of constructing the new chamber, it's whether it's worth it to you to have it externally. Some water companies may insist it's moved so they can access it in an emergency without coming inside your house.

Best bet is to talk to them, my local one has a Developer Services helpdesk that can answer queries.

We want to do the same. We have been advised that it’s likely to be more expensive because the foundations need to be built differently - below the waste water pipe (I think), rather than on top. We will need to get permission from the water board. We will need internal access.

@NothingIsWrong thank you. Very informative.

www.thameswater.co.uk/developers/larger-scale-developments/sewers-and-wastewater/build-over-or-near-a-sewer

It is Thames Water. Here is a leaflet I found.

www.thameswater.co.uk/help/home-improvements/building-near-pipes

Or this?

I reckon you will get build over consent fairly easily and may well get permission to move the access point (the drain appears to be straight at that section so it might not matter much).

Would probably be worth talking to the water company about logistics.

OP, you want the second link (the other one is for housing estates etc.).

I am in a terrace that predates running water and the sewers run through every back garden close to the houses.

Wessex Water took the view that, as long as some of our neighbours had access, we didn't need to keep ours and could extend over. Building Controls had to sign off before we poured our slab.

I am pretty certain we just supplied drawings and application form and a cheque for about £100. We asked our architect/quantity surveyor to submit it.

We did this but had to get permission from the water company. We had to pay a fee and they sent a man out to inspect the works and gave us written permission
The architect alerted us to this and arranged it

We moved the manhole cover into the alleyway at the side of our house (which we also own) as they still need access to inspect.

I moved a shared drain and manhole, it was really straight forward. Didn't have to pay anything to the water company, don't think they even came and checked the site. I did have building regs for everything.