Calculating the Water Flow Available
Start by calculating how much water flow you have available (and in turn how many drippers and sprayers you can operate at one time). To do this, simply run water from your faucet into a 5-gallon pail and time how long it takes to fill it. If it fills in one minute you know you have a flow of 5 gallons per minute (or 300 gallons per hour); if it takes 2 minutes, it’s 2 1/2 gallons per minute flow (150 gallons per hour), etc.
Remember that if water is being used elsewhere in the house (a shower or dishwasher, for example), it will significantly affect the flow to your irrigation lines.
If you can, it’s wise to leave a 25% buffer for other water demands.