Use unmarked drain for extension

[JimExtension]

Hello,
Hoping someone might be able to help with our drain connection idea.

We currently have a private drain that passes behind our house over to our neighbours garden that is marked on the Thames Water plans. From our neighbours garden it then goes into the main sewer.

We'd like to do a rear extension, adding in a shower room and moving the kitchen, which would result in building over our private drain and making new connections into it - it seems like it would be quite messy pipe wise, and non-ideal to have so much piping buried under the extension.

Our house does however have a second private drain connection to the combined sewer (this area is all combined sewers) which is unmarked on the Thames Water plans. This drain is in a much better location for the planned work.

This unmarked connection is currently only used for garage and surface water, however as it all goes to the same combined sewer, would we be able to connect our old and new bathroom/kitchen piping to it?
Has anyone dealt with connecting to unmarked drains before?
Would we need Thames Water to add it to their plans?

Thank you.

 

[jeds]

If it's a private drain you can connect to it. My advice would be to cctv survey it to the main sewer before making a decision. If it's good, crack on, if not, ??.

 

[Hugh Jaleak]

Unlikely Thames will have every last section of drain on their plans, often it's down to the People on the ground to suss things out as and when the need arises. If it's private, then you don't need Thames permission, although Building Control may wish to inspect it, prior to connection.

I would dye test to ensure this drain you are proposing to use, does indeed connect to a combined sewer, and if so, I would also take Jeds advice of getting it CCTV surveyed to ascertain it's condition before connecting.

 

[plugwash]

I dunno what it's like in other areas, but the drainage plans I got from the water company when buying my house only showed the drains in the street, they didn't show any of the connections from individual properties.

 

[bernardgreen]

My advice would be to cctv survey it to the main sewer before making a decision

Jeds advice is very sensible.

(1) A local building had a new staff washroom and toilet installed, The builder connected the drains to a convenient 4 inch sewer pipe and everything seemed OK for a few weeks. Then sewage started coming out of an inspection chamber,

The convenient 4 inch sewer pipe ended in a soak away,

(2) This mystery sewer / drain pipe was discovered when the gas pipes in the village were being replaced.

It appears to head uphill under the pavement directly towards the lounge of my cottage. ( bottom of picture ) and slope down towards the High Street ( top of picture ) and possibly the main sewer.

It is however not mentioned on any of the data / plans / documents for the area.

,

A bit more excavation uncovered a bend in the pipe that turned it away from the cottage, Through a crack in this elbow it could be seen that the pipe was half full of mud/sludge. Anglian Water came out and decided it was probably a redundant drain that might still be connected to the main drains but without getting a camera into the pipe they could not give a definitive answer.

It is now buried.

 

[jeds]

I dunno what it's like in other areas, but the drainage plans I got from the water company when buying my house only showed the drains in the street, they didn't show any of the connections from individual properties.

That is quite typical. I get a lot of water authority asset plans and they are highly variable. Sometimes nothing at all, and even fairly new estates will often show sewers but they can prove to be 3, 5, 8 meters from where shown. People don't always appreciate that even (public) sewers not shown on plans are still the responsibility of the water authority, so you have to be careful.

 

[JimExtension]

Thanks all for the advice. Getting the CCTV survey and verifying that the unmarked pipe does indeed connect to the main combined sewer is what we’ll go ahead with