Check Valve Problem - I think?

lbk said:

I installed a high quality check valve near the base of my sump pump - its not one of those flapper check valves. It worked perfectly. Really quite, no backflow at all. Then, I installed a battery backup pump and I used the same style check valve near the base of that pump. Now, when the main pump shuts off, its like I have no check valves at all. The whole system gurgles and you hear water and air moving back through the pipes. I tried multiple positions for the check valves, and nothing helps at all. If I disconnect the battery back up and plug the pipe, everything is fine - no noise at all.

What could cause this. Its not a faulty check valve, because I've tried several of them and it makes no difference. Any ideas on this?

Thanks.

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