Since I know at least one person is interested, I will describe my DIY PVC overflow. My design is based on this thread but I have made some changes.
$15 PVC Overflow Thread
Now, for my version. Since I don't have any pics I made a nice pretty solid model.
Components:
(1) 1" Cross
(1) 1" Plug
(2) 1" Pipes ~ 2.5" Long
(2) 1" to 3/4" Elbow Adapter
(2) Drain Pipes 3/4" X 5" Long
(4) 3/4" Elbows
(6) 3/4" Street Elbows
(4) Siphon Pipes 3/4" X 8" Long
(2) 3/4" Tee
(2) 3/4" Plugs
(2) Overflow Pipes 3/4" X 7" Long
Not Shown:
(2) Airline check valves
(1) 1" pipe ~ 3" long
(1) 1" Slip X FPT Adapter
(1) 1" MPT X Barb adapter
(1) 1" Vinyl drain pipe
So, to put it all together, I did things in stages to keep things square. First I glued the street elbows into the regular elbows and tees, pressing the glued pieces hard against my work table to make sure they were square. I then fitted the short 1" pipes into the cross. While that dried, I drilled the holes in the 3/4" plugs for the check valves by stating with a drill I knew was too small and stepping up one drill size at a time. Initially, I didn't have any super glue so I just press fit the check valves into place until I had the glue. Otherwise I would have glued them in at this point. Next, I glued the two siphon pipes into the tee and elbow. Then the 1" X 3/4" elbow adapters were glued to the cross making sure they were square and glued the 1" adapter to the bottom of the cross. I also glued the drain and overflow pipes into their two elbows so that the street elbow drained into the regular elbow.
Now, to keep things square I used the edge of my computer desk as it was just about the right width. I first glued each half together, first the parts inside the tank to the siphon pipe, then the drain pipe to the pipe coming out of the tee. Closing in on the end, I used the desk to connect the two wings to the center cross and made sure everything was square. Finally, I glued the 3/4" plugs with the check valves in place and screwed in the 1" barb adapter.
One item I didn't glue in place was the 1" plug. By resting the plug on the cross, I can not hear the draining water over the other sounds such as the skimmer and return pumps. Otherwise, you can glue this in and then drill a hole for airline tubing and a valve to fine tune the drain.
SO How do you fill this dang thing? WELL, I raised the end of the drain line until it was even with the top of the cross and then poured water into the drain pipe until I had filled the bottom of both sides of the siphon pipes. I had already attached a short length of airline to the check valve and by pulling on that airline with a 10mL syringe, I was able to pull all the air out of the tee.
Now, with the drain pipe running to the sump, I turned the valve on the return line to about halfway closed and started up the pump. I then adjusted the valve until I get a nice smooth cone of water flowing across the top of the overflow pipes and down into the overflow.
This overflow works because the siphon pipe ends remain submerged. The water drains down to the bottom of the cross both inside and outside of the tank. When the return pump starts, the rising water level allows water to drain into the overflow pipes, where it then gets carried by the siphon pipes over the rim of the tank and then drains through the cross and into the sump.
Every day or so I use the syringe to empty the air out of the top of the tees. I typically pull 10mL per day but I feel that there is more then enough extra room should I miss a day or two.
Simple, easy to make and inexpensive. Oh yeah, and IT WORKS!