Satellite septic pump systems like yours always have a $25 check or flapper valve installed in the line just above the pump that keeps all the septic semi liquid waste from return flowing back downhill like a siphon drain.
Heavy rain fall soaking the leach field above can cause a system to drain down especially when the leach field turns into a large frozen puddle.
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... down and out, liv'n that Walmart side of the lake!
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