2 check valves on 1 line ok?

I just replaced my sump pump. I put in a 1/3 HP Coleman (little giant) 50gpm @ 5' w/ 1/2" solids ok, replacing a functional 9 yr old hydromatic with a diaphragm switch. (9 years of use seemed to be pressing my luck ... mostly spring and summer rains)

The existing pvc line had an in line check valve. I left it in place so that when the new pump is replaced someday, it would be less messy when removed.

I also used a screw in check valve. I did this because I had one laying around, I didn't have a pvc connector for the pump, and it made the pvc connection to the pump very easy.

I chose not to use the pvc pipe from the old pump. I wanted to keep the old pump assembly together in case the new pump failed prematurely. I wanted a quick, drop in replacement to be available.

Thus, I have 2 check valves on 1 pump. It tested ok and was very quiet. Unusual, yes. But it makes sense given the description above.

Can I anticipate a problem from having 2 check valves on 1 line?

Also, is this new pump any good? It boasts lifetime warranty. How long can the old hydromatic sit on a shelf before it goes bad?

answered my original question

To answer my original question ... Probably not ok.

Theoretically, it works. On the downside, it created drag on my Big Dog pump that was obvious. I went back to a traditional install with 1 in line check valve and a 1/8" hole to prevent air lock and it gained noticeable capacity. The primary pump also uses a traditional configuration now.

I'm not sure I understand why screw in check valves are sold. They capture the imagination, but don't work very well. However, the only way you can figure that out is by experience. I'm also not sure how they deal with the potential problem of air lock. I couldn't see any ventilation methods. Perhaps they are not needed with that configuration?