Extending a drain run

[geebs]

Hi Everyone,

My 1930’s house has an old extension at the back and lean-to garage at the side. We are on a combined sewerage system. The drain runs straight along the side of the house in the garage. Rain water gutters for the rear of the house feed in a shoddy way through the rear wall of the garage to the open drain, also in the garage.

I need to improve the drainage situation at the rear of the house the guttering arrangement is poor. I also get a sizeable pool appear near the patio after any significant period of rain that is against the wall of my lounge.

My question is how feasible is it to extended the straight drain that runs down the side of the garage so it starts outside in the patio? The length of the extension would be around 3m.

This could then make it possible to install a french drain or slotted channel to stop water pooling near the property. Currently there is no drainage at the back of the house and the garden slopes down towards the house, so there needs to be something put in place.

 

[Hugh Jaleak]

Main drainage run is at the front or back? Provided the existing pipe isn't almost out the ground at the top end, it's simple enough to connect onto it, especially for rainwater, if you're happy to dig the garage floor up to do it!

 

[geebs]

Hi Hugh. Thanks for replying.

Main drain is at the front, it all runs down from the back to the front of the house.

The existing pipe is about 50cm deep from floor level. Is that deep enough?

I don’t mind digging up the garage floor, with the mess of pipes I’ve got going on there at the moment it would actually be an improvement!

 

[^woody^]

Just get some koi, it will be easier

If you have the falls then yes you can extend and connect to the front drainage. Otherwise, it will need a soakaway in the garden away from the building.

 

[Hugh Jaleak]

The existing pipe is about 50cm deep from floor level. Is that deep enough?

I don’t mind digging up the garage floor, with the mess of pipes I’ve got going on there at the moment it would actually be an improvement!

Yes, that's fine. Just carry it on as required, only need a 1:100 fall if carrying rainwater, (would need to look at increasing that if carrying soil/waste).

 

[geebs]

Great! Thanks for your help. It will be a weight off my mind sorting this all out!

 

[Captain Nemesis]

Are you allowed to just add new surface water connections to the sewer system without permission?

 

[23vc]

Are you allowed to just add new surface water connections to the sewer system without permission?

If it’s draining off roofs that are original/been there for years, and he’s teeing into his own drain not anything public, can’t see an issue. It’s more if it’s a new build extension that you might need to go the soakaway route. Then again strictly speaking yeah it may be notifiable to BC

 

[VDubDan]

Are you allowed to just add new surface water connections to the sewer system without permission?

Purely anecdotal but when I spoke to the BCO about my small extension he just shrugged and said connect it to the existing shared sewer. Didn't seek any sort of permission and they've signed off drainage now.

 

[Captain Nemesis]

OK.

I've been talking to my council about an extension and they want a soakaway.

 

[VDubDan]

OK.

I've been talking to my council about an extension and they want a soakaway.

I think it's just a matter of size and reasonableness

 

[23vc]

OK.

I've been talking to my council about an extension and they want a soakaway.

I’ve had it where the extension replaced a collection of outbuildings/garage (draining into the existing run) which were “roughly” the same roof area as the new extension give or take/being a bit creative, so used that argument to not do a soakaway.

 

[Captain Nemesis]

That's given me a useful idea. I'm not opposed to the idea of a soakaway (apart from the cost), but I'm on London clay so it might not work well.

 

[Hugh Jaleak]

Should apply the Drainage Hierarchy when deciding what method to use. First, a Soakaway. If this is not feasible due to space limitations, ground conditions etc, then second option is a surface/storm water sewer. If again, this is not practical (or available), then as a last resort, connection may be allowed to a foul or combined sewer.

The OP is already on a Combined System for the rest of the property, a bit more wont be noticed. If it throws it down with rain in Biblical proportions, (we had 50mm in 24 hrs round here on December 23rd), it'll be lost through a Storm Overflow anyway.