Do I really need a check valve on return lines

[AZMSGT]

If the sump can handle the back flow, there is no need for a check valve or any other device. Just because one person “recommends“ something doesn’t make it needed. No Red Sea tank needs one in a stock configuration.

As a matter of fact, I prefer the water volume decreasing in my tank when I shut off the pumps. This way I get a lower water level in case a fish tries to jump while I’m working in my tank.

 

[Billdogg]

Check valves require the mechanism to seal in order to work. However, microbes and other critters such as tube worms and sponges grow just about anywhere, including on valve sealing surfaces. Given this, check valves are much more likely to leak if not outright fail. I’ve never used one and never will.

^^^This^^^

Never used them, never will. If your sump overflows when the power is off, it is not properly designed and needs to be fixed. Check valves are NOT the answer

 

[naterealbig]

Do I really need to use check valves?

If my sump is large enough to handle the back flow of water? Using 2 DC pumps....

The “right” answer in know is yes, but I’m really trying to avoid them if I can. Added plumbing. Possible failed point in future. Difficulty servicing.

Does anyone NOT use them?

And if you say yes; type, style, brand please?

I agree with everyone's sentiment, with a caveat. While check valves may be a poor solution as a siphon-break, there may be other reasons you want to use them.

I run two return pumps in parallel on my system for redundancy. If one pump stops for some reason, the water can be pumped from the working pump, back through the non-working pump. Without a check valve downstream of both pumps, this could potentially prevent water from reaching the display.

Check valves work extremely well for this purpose. While they do foul over time, I am not concerned with a minute amount of water making its way past the check valve. It does however, keep the majority of the water from back flowing through a de-energized pump, and diverted to the display.

 

[h2so4hurts]

No, they can clog and will not be able to seal after a few months of growth. If you must use them, put them in with a union and use threaded check valves so you can replace them when you notice they stop working or restrict the flow from your return pump too much. I've always just built a sump that's big enough to handle the overflow. Also, if you're worried about your skimmer overflowing, spend $50 on a float switch to kill the skimmer when the cup gets too full. Everyone with an external skimmer has these installed and there's a good argument to have them on internal skimmers too.