Arvo All,
Two major leaks have been detected.
One at a joint in the 2" main at the rear of the house. The main is 500mms
down and would have made the leak difficult to detect.
The other was in the front yard at a crossover where the 1 1/4" main fed two
1" feeds to a sprinkler line either side. When originally installed, a
Conifer was planted immediately above it shortly afterwards. Eight months
ago I removed the 40 foot tree and digging through a maze of roots, found
that the original crossover joint was covered by the old stump and only just
visible. It was impossible to get at but was the source of another major
leak.
Now the main has been re-fed and is on top of the old stump (not pretty) but
the only way it could be achieved without a heck of a lot of work and
creating two new feeds.
My retic man then showed me just how much water was leaking up the side of
the pop-ups. Now they have all been replaced and everything seems to be
jake.
I fell base over apex by putting my foot into one of the bomb craters I had
to dig all around the front yard.
Today I'm resting.
There is a two inch GI pipe down the hole and a flange or something which
stops a string being lowered any further. Opinion has it that the
obstruction is the top of the spear/non-return valve. No wiser! The
neighbour whose bore is right over the fence from mine tells me the water is
down to 12 1/2 feet at the moment.
Thanks for all of the help and advice.

Cheers,
Don