There are many different options where you can gravity flow your bottom drain to.
Bottom drain gravity fed pond filter setup.
The term bottom drain is really a misnomer.
The fewer bends the better.
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.
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.
You then have a pipe from the ponds bottom drain sloping downwards underneath the filter then up and into the top of the filter.
If a straight shot is not possible use 45 degree elbows to raise or turn the pipe rather than 90 s.
All chambers except ch4 have 3in.
There is a waterfall 2 venturis v 2 bottom pushes bp a surface skimmer sk and 2 bottom drains bd in the pond.
There is an additional chamber the dry sumpattached to the filter.
Put the bottom drain and all the pipework in place to check all the measurements before gluing.
The main filter consists of 5 chambers ch1 to ch5.