Using the 3/4 inch as a backup seems like the easiest option. The only thing I'm worried about is how much flow I would be able to put through that single 3/4 in hole. It would be 3/4 then a T on top (pretty much the way its set up now) . I want a sump to increase water capacity as well as turnover rate. I currently have an fx6 plumbed to the overflow but I want to run a 1500gph return on the sump. Do you think 3/4 would be enough to handle it? Also the holes are already drilled pretty close together i think if I increase the size the bulkheads would interfere with each other.It makes a lot more sense seeing your pictures.
If it were me I would consider opening one of the 3/4 bulkheads up to 1-1/4" as an emergency overflow. If you want to run your returns through the overflow box (makes sense for neatness and keeping the tank from being cluttered) I would open the second 3/4" bulkhead up to 1" and use it as a return with a Tee at the top to split it into two 3/4" return pipes. When I say "opening up the 3/4" bulkhead" I mean remove the 3/4" bulkhead, drill the bulkhead hole to accept 1.25" or 1" bulkheads, then put the new large bulkheads in with the associated plumbing. Acrylic is pretty easy to drill. When I enlarged the bulkhead holes in my 180g this is how I did it: https://www.monsterfishkeepers.com/...bottom-planted-tank-build.714316/post-8188643 I just used a piece of scrap wood with the size of the new bulkhead hole in it as a guide to drill the bigger hole in the acrylic.
It looks like your 1-1/4" overflow pipe is constricted into a 1" pipe at the bottom. This will have a big impact on your maximum flow through that overflow pipe.
A simpler approach is to use the capped off 3/4" bulkhead as an emergency overflow and keep the other two as they are. There would be no new holes to drill.
What is your goal? If it is just extra flood protection use your current capped 3/4" bulkhead as an emergency overflow and call it good! If you want to increase the water turn over in your tank (more GPH) then I would enlarge the current bulkheads as described.
Like Egon I like bio towers (trickle filters, wet dry filters). I am implementing something similar in my 180 build:
Need help with sump setup
- Thread starter Drips702
- Start date
Ahhh... the FX6 is a closed loop hydraulic system. It actually sucks the water down the overflow tube as fast as it returns it to the tank. Since the water is under pressure through the whole FX6 loop it is pulled/pushed through the plumbing.
I am a VERY big fan of sumps. I think converting your tank over to a sump is a great idea and quite beneficial in many ways. With a sump you are depending on gravity to force the water down through the overflow pipe. For the couple foot drop in water elevation the water pressure will be minimal and and the flow will be greatly reduced from your current closed loop.
Another problem with gravity fed overflows is they have a high propensity to gurgle and make a lot of noise. There are several designs to reduce and practically eliminate this gurgling noise. Most of the designs use all 3 pipes as part of the overflow. Google "Herbie overflow", "Bean animal overflow" and "Durso overflow" for an explanation of each style and their advantages/disadvantages.
https://blog.marinedepot.com/education-center/charts-diagrams/durso-herbie-bean-animal-overflow
If it were me I would enlarge the bulkheads as described. BUT I always overbuild everything, so it would probably be best to solicit the opinion of another aquarist on the pipe sizes needed for the flow you want.
Water flow rates through PVC pipe based on water pressures: https://flexpvc.com/Reference/WaterFlowBasedOnPipeSize.shtml
