The sewer trick
Sewer charges are usually billed on water used, on the assumption it goes down the drain. Pool water doesn't. Many utilities give a one-time sewer credit for a pool fill if you call before you start and give them the meter reading. That can cut the bill nearly in half.
Hose flow
A standard 5/8 inch garden hose on typical house pressure delivers 8 to 12 gallons a minute. Time how long it takes to fill a 5 gallon bucket and divide 300 by the seconds. Two hoses on separate taps halve the fill time.
Water delivery
Bulk water trucks carry around 6,000 gallons and charge roughly $200 to $500 a load depending on distance. For a 20,000 gallon fill that's often close to the hose cost, done in an afternoon instead of two days, and it skips the sewer charge entirely. Start from the volume calculator if you're not sure of your gallons.