sump pumps and back siphoning

Group,

I'm setting up a sump tank for the first time. I have a CPR Overflow box, which works well. Right now I'm using my canister filter to pump water back up to the main tank. This setup works well, and does not overflow when the power is turned off and restarts by itself when power is restored. However, I'm worried that my filter is not working as well as it should since the flow rate is reduced by the head pressure and because only surface water which is skimmed into the overflow box and sent to the sump is actually being filtered. Is this a problem?

So I'll probably get an additional pump to move water from the sump up to the tank. Do water pumps have a problem with back siphoning and require a check valve? Or do they only allow flow in 1 direction and I don't need to worry about a check valve and back siphoning? I don't see this mentioned when looking at some pumps listed at marinedepot.com.

Regards,

Yes, water pumps do back syphon.. We use them at the pet store to fill tanks and i found out the hard way when i left the end of the pump in the tank and shut the pump off and the tank began to empty right back into the bucket. I would recommend a valve, we do have valves but i didnt know that it would back siphon like that so i didnt turn them off or take out the end of the pump.

Mike

All that tech talk about pumps coonfuses me. I bought a$20 carbon filter pump thing for my marine tank 3 years ago and that's all I've needed. My tank is 55 gallons. I set up another 1 year ago with the same pump/filter and it seems fine too.