"Dave" wrote in message
om...
Moved into a new house, the lawn has under grass drainage pipes which
start about 3 inches deep at one end and run to about 12 inches deep
at the other. The low end used to run into a natural drainage ditch
with a hedgrow growing within.

I assume this used to work great but we found out that just before
selling the house they put up a fence at the low end and backfilled to
level the lawn. The problem was that rather than poking the drainage
pipe out under the fence (and into the ditch) then simply covered it
with top soil leaving the end blocked.

To add to this there is a lot of clay around. I believe there are
several feeder pipes into this main pipe, not been hunting yet though.

My questions are; how deep should this pipe be at it's shallowest and
deepest? Should it be surrounded by gravel, if so to what diameter?
How may branches should it have or is it a case of the wetter the
ground the more pipes you put in?

Many thanks.

Hi Dave,

3 inches on the high side sounds a bit shallow, especially if you want to
airate the lawn. Drainage is really dependant on how bad your flooding gets.
The size of the drain system would be based on the area of lawn. Yes the
drains should be surrounded by gravel, to allow rainwater into the pipes
whilst preventing soil entering.

If you are not having problems with rainwater failing to soak away I
wouldn't worry about it. Although if you can remove the blockage from the
low end you'll probably prevent the drainage system back filling with soil
and debris.

HTH

Nick
www.ukgardening.co.uk