Sump pump air lock question

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Well-Known Member
Feb 22, 2019
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Hi guys,
So this one is kinda weird to me which is why I'm hoping someone can help me understand or have a theory on how this occurred....
Just yesterday I replaced my primary sump pump and redid all the pvc work so each pump had its own separate discharge all the way out the house and installed new check valves. Drained pit shopvac it super clean as well and cleaned backup pump. After all was complete I threw a hose via old washer hook up, in the pit and filled it to test everything. New pump performed about 10 times flawlessly. The float is non adjustable so I made sure the "off level" was not below the intake of my backup pump or I'd have to brick it. But everything looked great and off level was still about the backup's intake.

I unplugged the new pump to test backup which has a weeper drilled in discharge line too and she kicks on and BAM ...nada! She's ticking but no tocking, she's locked!

This 2 yr old pump has never air locked on me so why now? Why even having a clean weeper on discharge? Could it have been because the new discharge pipe was empty as this was the first fire up since reinstalled. I immediately unplugged her and re-fired up primary again, didn't know what else to do, pit was pumped down to normal pump off level and i then heard a quick gurgle but not sure which pump it came from because the backup pump doesn't make that gurgling sound after it shuts off like the primary pump does.

Attemped testing that backup pump a second time and it worked like a charm, like she always has in the past. Tested about 10 goes and all was good. Ran primary again between tests to make sure it wasn't to blame and the backup was still good a third time. A very strange air lock scenario here. Any thoughts are appreciated. Thx