Cost Of Moving A Drain

[mandimoo]

we are so far down a journey of purchasing a house with fantastic opportunity to biuid a single story rear extension. we are already financially committed to this purchase in terms of mortgage application fee, homebuyer survey and mortgage advisor (slightly complicated situation). we've just had the sickening realisation that there is access to public sewer, right in the middle of our proposed extension. am I being fatalistic in thinking we should walk away? brief background is that we have not got a bargain buy, but neither have we paid over the odds. we can just about afford a straight forward single story extension as long as we don't have loads of unseen extra costs thrown in. please can someone give me a bit of perspective?!

[The Builder]

First off, Mandi, are you certain it's public? Do other properties use it? If it's yours alone, then there's usually no problem overcoming this.

If others use it, then it is now the property of your local water provider. They must be notified if building within 3 metres of it. They don't like building over sewers for obvious reasons... access for cleaning etc.

Can you confirm which it is?

[mandimoo]

Hi, yes it's public and runs along the rear of the properties in the row.

[The Builder]

Ok, so the Water Company will need to be told. First step is to contact them and someone will come out for a look.

Depending on the circumstances, they may offer two choices. The first is to divert. They will usually carry out this work themselves, and bill you. They'll give you a quote.

They may allow overbuilding. It's at their discretion entirely. In this case, they probably send a camera down the line to check that everything's Ok with the sewer.

Siting inspection chambers at the entrance and exit of the run under the building would deal with access for cleaning etc. Bear in mind though, that, in the most unlikely event that the drain collapses and needs replacing, then it is possible they may have to do this even if demolition is needed.

I'm just thinking out loud now, but a technical solution may be possible. To lay cables etc across a road, they are often laid in a duct. Cables can then be drawn out and replaced without digging the road up.

I'm wondering if something along those lines could be used here. Maybe excavate the run under the extension, and lay in a plastic duct. This could be a 225mm plastic drain pipe. A new piece of 100mm pipe could easily be run inside this. To replace it would simply involve drawing it back out and poking a new one inside it.

Technically, anything is possible, but it's their decision. Before you commit, get their advice and their quote.