There are many different options where you can gravity flow your bottom drain to.
Bottom drain gravity fed pond filter setup.
Constructing a gravity fed bottom drain pond filtration system the theory is fairly simple really you basically have two areas of water the pond and the filter whose water levels need be parallel.
The main filter consists of 5 chambers ch1 to ch5.
All chambers except ch4 have 3in.
Dig out the trench for the 4 bottom drain pipe and run it all the way to where the rest of the filter system will go.
They should be more aptly referred to as a bottom filter feed or supply while a pump in the pond is aesthetically unattractive and can t remove large debris a 4 inch bottom drain can take large leaves as it continually vacuums your pond.
Put the bottom drain and all the pipework in place to check all the measurements before gluing.
Over a 1000 gallon pond powered with 55 watts and 25 watts waterpumps.
There is a waterfall 2 venturis v 2 bottom pushes bp a surface skimmer sk and 2 bottom drains bd in the pond.
The fewer bends the better.
You then have a pipe from the ponds bottom drain sloping downwards underneath the filter then up and into the top of the filter.
There is an additional chamber the dry sumpattached to the filter.