"Theo van Daele" wrote in message
...
The possible caveat with that is - as I sadly know from experience - if
the
spilled water flows back *under* the liner (if you work with a liner) it
pushes the liner up which pushes the water up to reach the pump, flows
back
under the liner... you get the idea I completely drained (no water
left
at all , maybe 50 gallon) a 6000 gallon pond in about 7 hours ...

I was just lucky to have this happen before I put my fish back into the
pond.

I now have the pump 40 cm from the bottom, but with a very large rock
(yes,
I know) underneath so that if the same ever happens again, the liner will
not just float on top but will be kept down (a bit).
snip

Theo...I speak from experience. If your 'rock' cannot be described as 'a
boulder', 'it took 5 of us to move it', 'and then the back hoe put it down',
or 'as big as a volkswagon'...IT WILL NOT hold the liner down. I had
probably close to 100 lb's of rock on my liner before the pond was done, and
my VF lifted ALL of it out of the ground.

Water is stronger then the hulk AND spiderman.

BV.