The maximum LISTED flow rate for a TA60 is 60GPM; the maximum flow rate for GOOD effluent water quality is 35 - 40 GPM. When you run the filter at the LISTED flow rate or higher, you will force fine debris THROUGH the filter and back into the pool. But, at 30 GPM, a sand filter with proper filter sand will produce water clarity close to what a DE filter can achieve.

A 1HP Whisperflo will generate somewhere between 60 & 80 GPM on a typical layout with 2" pipe. If you replace the pump internals with the parts from the 1/2 or 3/4 HP models, you will lower your flow, lower your electrical use per hour of operation, and improve the quality of water leaving the pump.

On an 18,000 gallon pool, operating at 35 GPM, you'd need to run your pump at least 8 hours.