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Solve Sprinkler Spacing and Pressure Problems with a Pitot Tube

By David Olson on July 20, 2016 in BlogNo Comments

Solve Sprinkler Spacing and Pressure Problems with a Pitot Tube graphic

PRIMG IR Pitot TubeTroubleshooting pressure problems in an irrigation system? The pitot tube can be your friend. Utilize this small, effective and easy tool to measure the velocity of moving water.

First, a brief history lesson: French engineer Henri Pitot invented the pitot tube in 1732, to measure the water velocity of rivers. The pitot tube has received some upgrades since then. Today, applications range from measuring the air speed of racecars and fighter jets (probably not happening at your jobsites) to testing nozzle pressure on rotary heads (much more practical for the landscape contractor). The name is pronounced “pee-toh,” by the way.

Make sense of sprinkler spacing and pressure with a pitot tube
Manufacturers base their sprinkler performance charts on the working pressure at the sprinkler. Once you identify nozzle size and working pressure with the pitot tube, you can determine the flow rate in gallons per minute and the radius by using the performance chart. With this information, you can better diagnose spacing and pressure problems in irrigation systems with rotary sprinklers.

PRIMG IR Pitot Tube

Measuring flow velocity with a pitot tube and pressure gauge.

How to use a pitot tube
The pitot tube can measure the flow velocity at a given point in the system, rather than the average flow velocity in the whole pipe. To do this:

  1. Attach a pitot tube to a 100 psi pressure gauge.
  2. Hold the tip of the pitot tube into the sprinkler’s stream. Hold it at a distance equal to half the diameter of the nozzle.
  3. Avoid inserting the tip of the pitot tube into the bore of the nozzle, as this will skew your measurements.

A word of warning: using the pitot tube can get wet and messy. Have a towel handy in case you get sprayed.

Go to Ewing for more troubleshooting tips
If your system is giving you grief and you’re unsure of the cause, your local Ewing store can help you find a solution. You can also watch this Ewing video to learn more about troubleshooting pressure problems in a sprinkler system:

Solve Sprinkler Spacing and Pressure Problems with a Pitot Tube graphic
David Olson
Find your nearest Ewing location at EwingIrrigation.com/locations.
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