David J wrote:
My water rates invoice shows an (admittedly small) additional charge
for what is called 'surface water drainage' which is included in the
sewerage charge as 'foul & surface'.

Enquiries revealed that this was a charge for rain water running from
my drive onto the road. They admitted that they have no idea whether
it does, or not. In effect everybody is charged unless they can
successfully challenge the charge, in which case one of their
surveyors will have been to the property to establish the facts. I
reckon that my drive is level, with just a slope on the public
pavement onto the road level.

Question is: How can it be determined (unless it is raining) if a
level drive passes rain water onto the road? On both sides of my drive
are lawns, and surface water will also drain onto that. As the drive
is brickweave some of the rain will soak though the gaps. Many of my
neighbour's drives actually slope away from the road.

Isn't this just a big con by the Water Companies?

Are you sure you have the right explanation. I get a reduction in my
water charge because I have proved to the water company's satisfaction
that the rainwater from my roof doesn't discharge into the main sewer.

I was not asked whether the drive drained onto the road, It doesn't, the
reverse is more likely and did happen before I put in kerb stones
myself. During a recent cloudburst (best part of an inch in under 15
minutes) my neighbour's new shingle drive was largely washed onto his
garden and his garage flooded. It doesn't help that the nearest uphill
gully this side of the road is several hundred yards away.