Have an 1,800 gallon pond built 20 years ago. Initially thought it was a pure AquaScape design given the waterfall, 35' water stream and shallow pond. Filtration is limited to the skimmer (updated with new net, brushes and mat) and waterfall (added new 4 Matala mats and bio balls).
Last year I had all rocks removed from my pond. At that time, we found a white 2" pipe buried under the stones and muck in the deepest (30") part of the pond. It had a perforated cap to keep the fish out of the pipe. And it ran through the side lining of the pond and into the front bottom side of the Aquascape skimmer. You can see a similar set up a thttps://biologicperformance.com/pond-bottom-drain-to-skimmer/. This year I added an aerated Rhino Bottom Drain to see if it would enhance the cleaning as our filtration is limited to the skimmer (net, brushes and mat) and waterfall (4 Matala mats and bio balls).
Yesterday I found a mystery cover hatch below a piece of slate in front of the pond. It's sitting between the skimmer and contains a gate valve. Pulling it up does not create any pressure or appear to open any water flow. But it's a gate valve.
The other mysterious part of this pond's set up is the skimmer has a tee valve which routes water from the submerged pump at the bottom up and off the tee to the right up to the waterfall. The prior owner said the top of the tee's piping had a knife valve that would shut off the water flow up to the waterfall, but he removed it as he never used it.
The left side of the tee has an opening that runs outside of the skimmer box to the right and disappears under a very large granite rock. (Sigh.)
We tried to run a hose down pipe itself but it is blocked inside. Initial thought was it was a way to channel water out of the pond for a quick pump out, but with the pipe blocked that won't work now. And maybe the gate valve was a way to open up the pipe, but it doesn't seem to be.
Has anyone seen this type of configuration on a hybrid or other pond?
Sue