Hello Jon,

More questions ,

Is it better to put concrete over the entire length of pipe, from the BD to the filter or just cover the pipe with dirt and put concrete where the pipe exits the wall of the pond?
When I installed my BD I set it in a concrete around and under it. The 4" pipe that runs from BD to filter I poured concrete every 2ft. I then placed the steel mesh over the pipe and poured concrete floor

Should I add some type of rebar to the concrete?
Steel mesh/rebar is A MUST in concrete, without it nothing will hold the concrete when it's starts moving/cracking

Why put a plastic grate over the opening of the bottom drain, isn't it better to leave it open?
You can leave it open but you don't want your koi getting suck in in your BD ending up in your settlement

Is there supposed to be some kind of sump in the pond below the drain, or should it go directly to your settlement chamber? Why?
No. Everything goes to your first settlement. The purpose of the settlement is to trap all the solids like leaves, dust and fish poo. That's why you need a drain in each filter for maintenace

Jaylene (again)

rgds,
Jon(again)