First time turning on a return pump on a new tank is always kinda nerve-wracking
I started off with the tank full, and the overflow full to the top of the standpipe
Then I filled the sump to a level comfortable for me - a couple or more inches below full is a good start. Keep in mind that this is all you have in the system, so it can't get any higher right now
( unless your tank back-siphons during a pump off )
It's a helpful idea to make a mark on the outside of the sump at this point with a pen on some masking tape. This will show you where the on and off levels are relating to your pump
Then I turned on the return pump and went from there
I keep my sump as full as possible, probably the same as most, but I allow for an extra few gallons in case something unforseen happens when the pump (s) are off
Things to watch out for right now are;
-Return pump is too strong and overfills the overflow box, eventually overflowing the top of the tank
-When you turn off the return pump, the return pipe outlets back-siphon water from the DT and over-fill the sump
-The return area of your sump is not large enough and you run the pump dry ( not likely in most cases, but watch for it )
Have fun
