What pipe size is required for 1¼" hoses for runs between 20' to 80'?

The requirement for the pipe size when using 1¼" hoses for runs between 20' to 80' is based on ensuring adequate water flow and pressure to effectively function with those hose specifications. Using 1¼" diameter pipe provides the correct balance between maintaining sufficient water pressure and flow rate for the intended application.

Sizing the pipe to match the hose diameter helps to minimize friction loss over the length of the run. If the pipe were smaller than 1¼", it could restrict water flow, leading to reduced performance of the sprinkler system. Conversely, using larger pipe sizes than necessary could result in excess cost and complexity without offering any tangible benefits in typical installation scenarios for that hose dimension and length. Thus, a 1¼" diameter perfectly supports the requirements for those specific hose sizes and lengths.