What is the maximum volume of water that can flow in a 1-inch diameter pipe?

A 1-inch PVC pipe handles 58 gallons of water a minute at a peak velocity flow of about 18 feet per second. This is equivalent to 3,510 gallons per hour.

A 1-inch PVC pipe allows for a wide range of flow variation. At a low flow velocity of 6 feet per second, water moves through the pipe at 16 gallons per minute, or 960 gallons an hour. Average flow velocity of 12 feet per second passes 37 gallons per minutes, or 2,220 gallongs per hour. These flow rates depend on variables such as bends, fittings, pressure and viscosity. For example, as the number of bends and fittings increases, the flow rate decreases.