7ft Aquarium with Sump - Drain pipe/Ball Valve


Hi all. So I have a 240G with a 5ft Sump. If my maths is correct, my drain piping converts to 1.5in and my return is 1in.

I also have an 1.5in overflow in the tank that leads to the sump. I have a variable speed pump that I've got sitting at around 1320gph (5000 lph).

I'm finding that even if I push the pump up to 3400gph, I cannot have the drain pipe's ball valve open completely without it sucking air, i.e. it drains faster than the pump can refill.

So at 1320gph, I am having the ball valve about half closed, and while it isn't generating bubbles from sucking air, I find it makes distinct 'clicks/clacks' every few minutes - like you might expect in a submarine movie. :p

I've got an airstone pipe stuck in the top of the durso standpipe which seems to help with the gurgling somewhat as it breaks the surface and slows down the air intake (hole drilled in the top of the standpipe).

Any ideas about how to stop the clicks/clacks or if it's even possible to ever open the ball valve completely?


You could try putting a reducing coupling at the end of the drain pipe. Something to bring it down to an inch. If you're using one of those pvc ball valves, you could try swapping it over to a brass one. Might be stupid expensive for a ball valve that size tho. Maybe another type of valve would be an option, a multiturn valve?
  • Thread Starter


Thanks for the ideas. Unfortunately it's all plumbed in already. I have found after monitoring it further that this occurs when the water level fluctuates a bit. I have it running now where it is barely trickling into the emergency overflow and it stops the sound.

I'm also wondering why, after leaving it running 'perfectly' like that for hours, the water will then fluctuate...almost like the pump is taking a slight breather and reducing the return flow a little. I have a spare variable speed pump (both are manually selected, not auto in case anyone thought they're 'adaptive') so I might see how that one performs.
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