Berkeley SSHM-2 Pump Loses Pressure After Minutes: Suction Leak or Internal Wear

2 HP Berkeley SSHM-2 multi-stage pump. Furthest head 325 ft, 40 ft elevation. Zone runs few minutes then loses pressure/flow to zero. City water works fine → not valve issue. Flow at pump 12-15 GPM. Pump too small?

Two Leading Theories

1. Suction air leak: Classic cause of prime loss after running.
2. Lake filter plugging: "Once the zone shuts down the obstructions drop off the filter." Suggests going in pond to watch filter while running.
3. SSHM-2 internal casing spin: "Has had some difficulties with spinning its internal casing under higher pressures. If it has ever gotten hot while running I would suspect this." Test: prime pump, run with tiny flow (1 sprinkler ~2-3 GPM), check discharge pressure. Should see 85+ PSI. If <80 PSI → internal problem or filter completely plugged.

Distance/elevation/GPM are correctly matched. The progressive pressure loss points to suction side or pump internals.