PlainBill wrote:

Wow!! A lot of misinformation here!!!

A given pump will be just as efficient if it is pulling water up from
a pond or pushing the water.

No, I'm just not buying that. Look at the edge case - if I have a
sufficiently powerful pump in the pond, I can push water up to any
conceivable height. If I have a pump outside the pond, at the top of a
waterfall pulling the water, it is impossible to pump more than
approximately 32 feet - with _any_ pump. So it seems pretty evident that
any pump placed _above_ the water surface is going to be less efficient
than one below the water level (though not necessarily _in_ the pond).

A rule of thumb is the GPH rating of the pump should be twice the
capacity of the pond.

Odd rule of thumb. Another rule of thumb is 4 changeovers per hour, but it
all depends on the size of the pond. I'd want at least that rate for
anything under 500 gallons. I'd drop it to as little as half a turnover
for something in the 5000 gallon range.
--
derek