"Andy Dingley" wrote in message
...
On Sun, 13 Feb 2005 13:41:54 +0000, zaax
wrote:

Why can't surface water drains be connected it's only a tank after all.

A septic tank relies on a minimum holding time to let the bacteria do
their bit. More water into it means less time spent in there before
the outlet gets pumped / flows over the weir. If you start directing
a whole roof's worth of rain in there, then that can be several times
the capacity and you really do start to get carry over.

If the yank gets smelly in wet weather, you have a problem with this.

You'll also flood your soakaway if you have one. Surface water can be
drained into a watercourse but foul water can't.

Peter Scott