Sump questions

[itzclayyo]

Hello, I'm brand new to RC, and first I just want to say this site is excellent! I'm pretty new to reefing, only about a year in with a nano- so it has no sump.

This is going to be my first setup with a sump, and I'm a bit confused. Here's a drawing I made that might help explain my setup.

http://i517.photobucket.com/albums/u333/itzclayyo/filtration.jpg

Questions-
1-What will happen if only 1 of the pumps fails?
2-What will happen if both pumps fail?
3-Once the water line drains down and is bellow the TOP overflow cut-outs, will it stop draining into the sump?
4-Will the bottom overflow cut-outs let water through and eventually build up to drain down into the sump even once the top cut-outs aren't?

Thanks.

[pjf]

I’ve never tried your proposed setup so here are my guesses:

1. If only one of the pumps fails, it is likely that its sump will overflow because the other return pump will keep operating.
2. If both pumps fail at the same time, it is possible to avoid overflowing a sump by keeping the return nozzles high to avoid siphoning water back through the pumps. If your return nozzles are of different heights, most of the water will be siphoned by the lower nozzle and may flood a sump.
3. A pump return line will keep siphoning water into the sump so long as its nozzle is under water regardless of the overflow cut-outs. The water entering the cut-outs rarely overflows the sump. Water that flows through the cut-outs must still reach a standpipe opening to reach the sump.
4. I’m assuming that you have a Megaflow with top and bottom cut-outs. The bottom cut-outs are irrelevant. Any water flowing into the bottom cut-outs must travel up to the top of the inner Megaflow wall before entering the overflow. Once water enters the overflow, it must still reach a standpipe opening to enter the sump.