Pentair STA-RITE SAND DOLLAR Installation And User Manual page 16

Return flow to 1. Obstruction in the pump hair and lint
pool diminished,
pot.
low filter
2. Obstruction in pump.
pressure.
3. Obstruction in suction line to pump.
Sand returning 1. Broken underdrain lateral.
to pool.
2. Backwash rate too high.
Clean basket in strainer.
Disassemble and clean pump.
Clean skimmer basket. Remove obstruction in lines.
Open valves in suction line.
Replace broken or damaged laterals.
Reduce backwash flow rate.