"RichToyBox" wrote in message
news:keMda.129781$eG2.17274@sccrnsc03...
BV,

If the pump return to the pond is above water level, as in a waterfall,
then
a check valve would not be needed. If the return is below water level,
then
the top pond and bottom pond will try to equalize, with the potential of
overflow of the veggie filter and loss of water. Due to your design using
a
very small difference in elevation, a bottom drain and skimmer, your pond
and veggie filter will equalize whether there is a check valve or not.
For
you, I would say that you don't need one.

snip

I think I will be OK without one. I only need raise one edge of my main pond
up, and then the entire area will be level.

BV.