why not get make new fittings and bulkheads and get rid of the glued ones
Clint, This is in reference to your PM asking me what would I change about my plumbing if I have to do it over again.
I set out to design my plumbing to be as quiet as possible since this tank is in my small home office. I like the Bean Animal system the best and tried to have a modified version in my existing dual overflow system. The original Bean system requires all 3 drain pipes in the same body of water and is often associate with a long or coast-to-coast weir overflow for best surface skimming. Each Cornerflo of the Marineland 125g tank has two 1" holes designed for one drain and one return. There is simply no room to have a third pipe in the Cornerflo.
The Bean system has 3 drain pipes: Primary drain controlled by a gate valve, an open channel with an airline, and an emergency drain. While I can have the primary and open channel in one Cornerflo, the emergency drain has to be in the other Cornerflo. The emergency drain pipe must stand higher than the primary and open channel and is dry most of the time.
The above set up essentially shuts down one Cornerflo of the tank which I worry will not provide adequate surface skimming for the tank with only one overflow.
The purchase of the tank also includes two overflow plumbing kits, one for each Cornerflo. Each plumbing kit has one 1.5" drain pipe with double 90 degree elbows and one 1" return pipe. Each pipe is glued to a 1" bulkhead. I think the reason for gluing the pipe to the bulkhead so no water from the Cornerflo will get into the sump once the water level in the Cornerflo is below the pipe openings. If you don't glue the pipe to the bulkhead, all the water in the cornerflo, approx 3.5 gallons, will eventually leak into the sump below. Depending on your sump, it may not handle an additional 7 gal of water. The 1.5" drain pipe has an airline tubing at the top as well as two holes drilled on each side which introduce air into the drain to avoid a full siphon. If water level rises above the airline opening, full siphon will be triggered. This is a good safety feature to prevent overflowing the display tank as a full siphon of a 1" PVC pipe can drain 1700 gph. This is similar to the open channel in the Bean system. In normal operation, you don't want full siphon to occur as it creates a lot of noise like flushing your toilet.:lol2:
My current set up is not a true Bean system. In my right Cornerflo I replaced the 90 degree elbow (the one with holes and airline tubing) with a solid elbow so I can have full siphon but regulated by a gate valve below. I also remove the 90 degree return elbow from the 1" return pipe to serve as a backup drain. Since the 1.5" is my primary drain and at full siphon at all times, there is only a small amount of water getting into the 1" pipe. This side of the Cornerflo is completely silent.
Because I don't want to give up the skimming capacity of the other overflow, I simply install the factory plumbing kit as designed. It is still very quiet as long as I don't exceed 700 gph. Once exceeded, the 1.5" drain will go in and out of full siphon making a lot of noise.
I have two ways to control the flow rate to my display tank: 1) by diverting some of the return water back to the sump, and 2) reduce the speed on my adjustable BlowHole 1450 pump.
I hope this long explanation answers your question. I know you are new to the hobby and I tried to make it as clear as possible. There is nothing wrong to install the factory provided plumbing kits as they are designed. As long as you don't exceed the max flowrate each Cornerflo is rated for, you still have a reasonably quiet system with no fear of flooding your floor, assuming you have an adequate size sump to hold all water when power is out. Good luck with your 125g build.