need opinion on check valves

[hondo]

I am setting up an acrylic tank with twin overflows and was wondering what the general consensus was regarding check valves. worth putting in and work great, or not worth putting in because they really don't work.

 

[broomer5]

I don't use them.
Many folks do though.
If you can install unions on either side of check valve - and remove them occassionally to clean them - I would consider using them then.
If not kept clean - they can leak.
I would not rely on any check valve as my only means of preventing water siphoning back to the sump.

 

[rangermonroe]

Even if you decide to use check valves, do use a siphon break.
A small piece of coral, sand or stone lodged in the valve can cause it to completely malfunction. Wet floor, dead pump.

 

[dfimble]

Writting from experience, and a very wet floor... I would not use the closed kind of check valve, like you would find at Home Depot (all white with no way to see the valve). I would use the clear kind where you can see the valve. The one that I now use has a HUGE flap which closes with little back flow.
The problem I had was that the pump stopped the backflow enough to cause the check valve to fail. Thus a wet floor. It took a good 5 hours to drain the tank. The 55 gal drained down to the 5 inches of sand. All the fish found a nice puddle to flop in... and believe it or not all the corals withstood going completely dry for over 2 hours. Unfortunately the fish didn't make it past a week.
I would definately use one, a good one.
David