It sounds like his 1/3 hp pump, being discharged through a skinny garden hose, is pumping out the pit much faster than his 1 hp pump. I assume his main discharge is at least 1-1/2 pipe. So it sounds like there is likely a defect in the discharge line. Which is something I tried to bring up earlier. Just last weekend, I rodded out a buried 3 inch discharge line that tended to freeze and clog during the polar vortex weather. Even though it was set up to drain to daylight and not hold water. A pipe joint near the end had blown apart, the rubber coupling had rotted and failed, and water was just bubbling up through the dirt, not from the end of the drain that seemed clear and open. Or his check valve is defective, or maybe the spring flapper is broken loose inside.