drains in the back garden - not public?

aoleks

hi all,

I am looking to build a fairly standard single storey extension at the back of my house. permitted development and all that.

there are 2 "manholes" in my back garden, one under the proposed extension and another one further out to the back. I just spoke to the sewerage provider and they say they have no information whatsoever about those drains, hence they believe they're private. they also said as far as they're concerned, I don't need any permission from them to get the work done (building regulation excluded, of course).

is that even possible? could those drains be entirely mine (private)?

where can I get more info on this?

Le_Kirk

Have a look on your deeds, there might be a site plan showing the drainage in dotted lines.

Alter_ego

Are the drains shared with another property? If yes they are water company's responsibility

stuart45

If you can lift the covers it could give you an idea where the drains are coming from and going to. They might be coming from only your property and going to join a 6inch pipe along the back of the houses.

Section62

aoleks said:

there are 2 "manholes" in my back garden, one under the proposed extension and another one further out to the back. I just spoke to the sewerage provider and they say they have no information whatsoever about those drains, hence they believe they're private. they also said as far as they're concerned, I don't need any permission from them to get the work done (building regulation excluded, of course).

is that even possible? could those drains be entirely mine (private)?

where can I get more info on this?

The person you spoke to has given you bad information.

The lack of information held by the water company is not evidence they are private.  The vast majority of back-garden public sewers are not mapped, and the sewerage undertakers don't know about them.

That (possibly incorrect) information from the water company doesn't mean you can now treat them as private and do what you want - they are still legally public sewers and the legal requirements remain the same. If there is a problem in the future you'll almost certainly find that the information you received came with the caveat that it couldn't be relied on to be accurate and you should make your own checks on site (or request these to be done).

The correct advice is given in this thread already - you need to find out whether or not the pipes are shared with another property.

As stuart45 says, lifting the covers and looking at the pipes will give you an idea what purpose the manholes serve, but to be sure you need to get a drainage survey done.

Whether they are private or public you will need to know what the manholes are for and what condition the pipes are in, as your extension will be built over at least some of the pipes and the designer will need to make a decision whether to re-route or protect them.  To a degree you ought to be more concerned about your private drainage than the public sewers, albeit you don't need a formal build over agreement for the former.

As a former LA property there is a fairly high chance they were constructed with shared drains (now public sewers) - although whether or not your one does have shared drainage just comes down to luck with the way the original designer decided to make drainage provision for yours and the neighbouring properties.

aoleks

very helpful, as always. so if I understand this correctly, if I want things done properly and want to be 100% sure, I need a survey to confirm the nature of the drains. what's this type of survey called and do you have any idea what it costs?

thanks

Section62

aoleks said:

very helpful, as always. so if I understand this correctly, if I want things done properly and want to be 100% sure, I need a survey to confirm the nature of the drains. what's this type of survey called and do you have any idea what it costs?

thanks

The best approach is to get a CCTV drainage survey - get some quotes explaining that you need to find out where the drains are because you want to do some building work, and you also need to confirm whether they are shared or not, and whether you have combined foul and surface water drainage or separate. (the second manhole could be a soakaway)

In principle you don't need the CCTV element to find out whether the drains are shared/public or not (this can be done by simple inspection and/or dye testing) - but as you will be building over something, it makes sense to CCTV it.

I'd expect to pay around a couple of hundred pounds, depending on the area of the country.  I'd also tend go for a smaller company which promotes itself as a survey company, rather than a chain offering 24hour 'drain clearing' services who might do surveys as a sideline.

stuart45

You might have something like this. Pipes from bathroom, kitchen and possibly RWP going into first manhole and second manhole before common sewer.

Belenus

Lift the covers and see whether there is just one inlet and one outlet or multiple inlets and outlets.

If there is just a single inlet, get someone to flush toilets and run water down your shower, bath, basin and sink drains etc ands see if water flows through the outside drains.

If you get on with your neighbours, ask them to do the same and see if that also produces water flow.

That will go some way to determining if the drains are active and service which properties and perhaps give you some idea of what you might be facing.

You should still get a proper survey done but you will have done some of the work.

aoleks

stuart45 said:

You might have something like this. Pipes from bathroom, kitchen and possibly RWP going into first manhole and second manhole before common sewer.

thanks all for the advice. may I ask, if I have this setup, is it an advantage?

I got a CCTV survey booked in for next Thursday, I'll let you know what they say.

Section62

aoleks said:

stuart45 said:

You might have something like this. Pipes from bathroom, kitchen and possibly RWP going into first manhole and second manhole before common sewer.

thanks all for the advice. may I ask, if I have this setup, is it an advantage?

From the POV of doing building works on the house then yes, the advantage is the drainage you'd affect is your own private drains and no build over agreement would be required.

However, unless the length of the gardens is much shorter than implied by stuart's sketch, this kind of layout would be relatively unlikely as it requires a much longer length of pipe (and trench-digging) than alternatives which common together two or more houses into one connection to the main sewer.

It is an approach that some private developers might take (more likely in the past than now), as it means each property is responsible only for its own drainage, and it removes the complications that come with shared drains.  However, for (ex) LA properties that isn't necessarily a consideration, as the LA was typically building in the expectation that property maintenance would remain their responsibility on a communal basis - and therefore shared drainage was no more of an issue than shared roads and footways.