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Posted: Wed Mar 14, 2007 3:18 pm
by clowbeck
I had my drive relayed a couple of years ago. The drive slopes towards the front of the garage (15 degrees), with a drainage channel running in front of the garage door to carry run off water away. The lads who layed the drive installed a soak away running down the side of the garage! I've now noticed the bricks below the DP course are wet.
The only drain on my property is located beside the rear garage wall. Therefore the drain at the rear of the garage is at the same level as drainage channel at the front of the garage. The garage is about 7m long so how can I connect the two and still have an efficient drainage flow?
I was thinking of trying to install a small submerged pump (equiped with a float switch) of some sort between the drainage channel and the drain at the rear of the garage. The idea being that the pump will sit in a small reservoir / housing chamber and switch on during heavy rain or when cars are being washed.
Any experiences, recommended equipment or advice on this will be most welcome.
Posted: Wed Mar 14, 2007 4:44 pm
by Tony McC
I'm becoming increasingly worried about this practice of dropping in a linear channel in front of a garage, popping a hole in the bottom of one end and claiming it will "soakaway". It's shoddy and there's no other word for it!
First of all, the soakaway-ability of such a construction is unproven. On new-builds, the likelihood is that it will function for an initial period because of the loose backfill around walls and foundations, but on older properties, there's no guarantee that the sub-layers are even permeable. Secondly, the BRE advice is that all soakaways should be at least 5 metres away from any building. Having a linear channel outfall at the side of the garage does not meet this requirement.
If anyone is having this sort of arrangement installed, they should check with the contractor just where the outfall will be located and how that location will be capable of dealing with all the water directed to it.
Anyway: on to clowbeck's problem. Because most driveways deal with relatively small volumes of surface water, you can rely on basic gravity to get all the collected water from the front of the garage ton the back, even though it is, essentially, a flat bone.
If the existing threshold channel was to be extended around the corner, and then all the way along the side of the garage until it meets up with the one outfall point available, it WILL work. As water accumulates in the channel, it will flow along seeking to be as flat and low-lying as physically possible, which will cause it to "flow" along the entire length of a flat-laid channel until it comes to the outfall.
This principle of hydrostatic pressure can be used as long as the volumes of water are small and the length of the channel or pipe is relatively short. It's not a good idea for large volumes or long channels/pipes, but can be a useful 'workaround' when working with drioveways and patios.
Obviously, if a genuine 5-metres-from-any-building soakaway could be built, that would be a better solution, but mot many modern properties have the luxury of all that space.
Posted: Thu Mar 15, 2007 7:29 am
by clowbeck
Many thanks for your advice! You presumed right, I will just run a drainage pipe down the side of the garage (under a narrow gravel path to the rear of the house).
I will get cracking with it this weekend.
Posted: Thu Mar 15, 2007 1:05 pm
by Tony McC
Not pipe: use channel. It's much easier to install and to access if there was to be any problem.