Quick questions....RO filter and Sump

[fishman]

I have 2 questions...
1) Im building a sump out of a 20 gallon long tank. I want to build a top to it about half way across and then down into the sump to put a place for a drip plate and maybe put one baffle in. What parts do I need in order to plumb in the return from the tank to the sump? Do I have to use a bulkhead? I want to place one order for all of the stuff I need.
Does anyone have any plans/pics of the one you made?

2) I have an RO/DI system with three filters. When and how often do i change these out to make sure the water Im getting is pure? I had heard every 1000 gallons that you make. I have been keeping up with the gallons that I make, but this doesnt account for the gallons that is waste

Thanks

 

[darb2]

Bulkheads are the best way if your tank is drilled. If not you are going to have to get an overflow box. For the return you will need tubing or pvc to make the connections.
2 look on ebay for a TDS meter. When the mambrane goes the filtered water will have more tds.