Water Flow Calculator & Sprinkler Head Performance Tables

Measuring GPM and Psi

Finding your Flow Rate (GPM) and measuring the pressure at your Hose Bib (PSI) are the first steps in designing your sprinkler system.

Both PSI and GPM determine the amount of coverage you will obtain using a selected sprinkler head. After completing the worksheet (see sprinkler calculator provided below) you will be able to access the following:

  • Verify that all sprinkler heads in your system will have sufficient water flow.
  • Verify that you have enough PSI to extend or lengthen sprinkler system.
  • See how subtracting a head or adding a head might affect performance.
  • Find which kind of sprinkler head or nozzle to select before installation.
  • Estimate the coverage of each head and maximize your sprinkler layout.

The Lawn Belt Sprinkler Calculator

As you fill in the calculator make sure to click (or Tab) into each box from where specified. (using your Tab key will allow you to move down the sprinkler calculator, using your Shift and Tab together will move you up in the worksheet)

When re-running numbers,always start from top of sprinkler calculator and work down to refresh the new values.

Total zone length in feet (typically 50)  
Number of heads in your kit (typically 3)  
Size of your bucket or container (gallons)  
Time it takes to fill container (seconds)  
Click box to see GPM at Hose Bib  
PSI Reading at Hose Bib<(use gauge)  
Calculated PSI (w/ friction loss) -->  
Calculated GPM (per head) ----->

Note: When adjusting your values in the boxes, always click into top box of calculator and then down to refresh the new values. (Use Tab key to refresh. )

Rotor Head Performance Tables

Next take your Calculated PSI and Calculated GPM and find the minimum performance reading for the sprinkler head.

Remember you will need to look at both PSI and GPM readings to locate the correct sprinkler head / nozzle.

The following table represents the Orbit Rotor well sell at Lawn BeltUSA. These work well at both low pressure and high pressure.

The Orbit Rotors ship with free interchangeable Nozzle Inserts. By matching your readings from the sprinkler calculator to the correct nozzle you will receive maximum coverage for your system.

Looking at Table above you'll be able to see that to use a Orbit Rotor head you'll need at least 30 PSI and a GPM of .64 (see top of Table .red Nozzle)

For example if your PSI is 30 and your GPM is 1.4 you could use blue Nozzle w/Orbit Rotor.

If either your PSI or GPM are too low and you can find a head to match you may have to re-run the numbers in the calculator by either subtracting a head or shortening the sprinkler system.

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