The time it takes to fill a pool depends on the size of the pool and the flow rate of the hose used to fill the pool. The flow rate is measured in gallons per minute.
The Washington State University Extension assumes a flow rate of 18 gallons per minute from a 3/4-inch hose measuring 100 feet.
To determine how many gallons the hose pumps per hour, multiply the gallons per minute by 60 minutes. Eighteen gallons per minute equal 1,080 gallons per hour.
To determine how many hours it takes to fill a pool, divide the number of gallons the pool holds by the gallons per hour. At 1,080 gallons per hour, a pool holding 5,000 gallons takes 4.63 hours to fill.