My parents' new backyard pond (described in more detail in this post: startup for ornamental pond )
has two below-ground skim filter units installed, like this picture (which I hope has attached successfully to my post).
This is a Waterway product, apparently sold primarily for above ground pools. In this particular installation, there are two of these skim filters installed, below grade. The skimmers are along the edge of the pond, about 2 - 3 feet apart from one another, and both connected with a Tee to an underground pipe that runs to the pump.
To winterize this, would one blow out the pipe (one unit at a time) from the pump side, and then reach down to put a plug into the connection at the bottom of the cylindrical chamber that normally holds the filter cartridge? And should the whole container, from the filter space up into the skimmer then be treated the way a skimmer normally is treated in an inground pool (i.e. using something like the weighted empty bottles, or pieces of pool noodles, that I've seen recommended to protect skimmers against freeze damage)? I expect the pond water will be drained down to below the skimmer openings initially, but that wouldn't keep new water out of the skimmer and the lower filter container over the course of the winter...
Does anyone have any experience with a unit like this below ground? We have fairly cold winter climate here; I just looked up frost line, which is listed as 42" for CT. Normal water depth of the pond itself is ~20", in case that matters.