wildernet said:
Why do you say to use two instead of one with two standpipes and two U tubes.
The limiting factor at that flow rate will most likely not be the diameter or number of the pipes, although they will play a factor. It is the amount of water that will need to go between the "teeth" of the surface skimmimng activity of the return that will be a problem. You
could build an overflow large enough to handle the flow I imagine, I just hate to personally donate that much real estate to the overflow, especially when the corners are usually such dead spots in terms of overall tank flow and design. Redundancy is part of it as well, and it is just my personal opinion that at this flow rate, two would be better than one.
If you're going to make an overflow for that volume of flow, you can pull water from both ends of the tank to improve your exchange rate of pumped/sumped processed tankwater Vs. non-pumped/sumped unprocessed tankwater by using 2 overflows as far apart as is possible.
JMO.