Garage roof rainwater problem.

[Dan S. MacAbre]

My mum and dad's garage flat roof has a gutter at one end that runs via a drainpipe into a grid that just leads into a soakaway. Needless to say, said soakaway silted up years ago; and now, whenever it rains (which it has done rather a lot of recently), their patio floods nicely. The nearest downpipe from the roof goes between their house and their neighbour's between two conservatories, and wouldn't be easy to connect to (especially since the water would be required to flow uphill); but there is a soil stack about eight feet away. Can it be connected to that? Or is a water butt the best (and only legal) option?

[Davidm]

The whole rear roof on my Victorian house discharges into the main sewer, via a gully/trap where the kitchen waste water goes. Been like this since the house was built.

[Robin]

Yes but (a) there is a trap - and one which is relatively easy to clear of leaves, moss, dead rats and other dross; and (b) in later times many houses were built with separate rain water and sewage systems.

[David]

Leaving aside the need for some kind of cleanable trap to prevent sewer gasses leaking out, the answer is "it depends".

If the rain water from your main house already empties into the main sewer then it is probably O.K. to use the main sewer - but this is at the discretion of your local water authority.

If your main house drains into a separate storm water drain one or more soakaways then they are unlikely to permit you to use the main sewer. However you could always ask.

A water butt seems to me to be only delaying the problem. Once it has filled up then you will get exactly the same volume of water off the roof wanting to go to exactly the same place.

Fixing or replacing the soakaway is probably your best bet (but see above).

Oh, and on the subject of traps - normally a waste water trap outside is sunk into the ground and connected to the drain underground. Sinks and the like have a U bend trap fitted underneath then a direct connection to the soil pipe pipe (inside or out).

I am trying to find a reason not to fit a trap half way up the garage wall so that your gutter drains into it but you can still connect to the soil stack above the ground. As long as it is in a place where you can service it easily.

Cheers

Dave R

[Peter Andrews]

Water butts fill up, however if you connect a length of drip/leaky hose laid down the garden in a suitable location (a soak away without any digging) you can leave the tap turned on during the wetter months so that the butt drains out and can normally cope with the next rainfall without overflowing and then when it's drier you can turn the tap off to conserve the water for use when you need it.

Peter