Well - Actually, I've changed my mind and am now going to go with the
Aqua-Wizard retro drain above the liner feeding into the wall of the
pond.

It occurred to me that being in z5 - I got very concerned about
freezing lines/possible breakage. My freeze line here is 3 feet (from
what I understand). So in my mind, I'd have to either run a straight
horizontal shot from the drain (3.5-4' below) to an underground filter
(not going to happen) OR devise a way to close off & empty as much
pipe as I can where the pipe begins to rise... that I'd be
susceptible to cracks in the pvc with the freeze/thaw cycle.

Since trenching down 4' & sinking a filter in the ground isn't an
option. My only other recourse to prevent freeze cracks is to install
a gate valve WAY below the surface by the ponds edge & create a deep
well around it or diving in the pond, popping off the lid & plugging
the hole of the drain. I imagine this to be a nasty job to perform in
December or so.

I felt with the retro, I can reach in, pull off the retro & easily cap
the pvc hole in the wall - suck out the water - close the gate valve
at the filter.

I've done a few searches here and it does seem that freezing pipe is
an issue and people have had problems.

If my logic is misguided - please let me know.



Having both types, I'm glad you decided on the under-the-liner. As far as
the gate valve do make it so you can valve down or turn off the bottom
drain, the reason behind this is if you want to do a slow circ. in the
winter you can close down the bottom drain minimal to nothing and use just
the skimmer.