Impulse Sprinklers - Knowledgebase Question

Arcadia, Ca
Question by shwen8888
May 29, 2010
I use impulse sprinklers to water my lawn. My house inlet water pressure is set at 85 psi. I have a problem that some sprinklers stopped rotating after several months. The brass sprinklers stopped rotating normally within 2 to 3 months while those plastic sprinklers maintained normal operation for few more months. Is it because of low water pressure, or are there any other reasons?

Answer from NGA
May 29, 2010


There are a few reasons that impulse sprinklers will stop rotating and low water pressure tops the list. Most impulse sprinklers need at least 25 psi at the last head in order to work properly; Remove sprinkler head and attach pressure gauge to riser. Check operating pressure with line running. If pressure is low. check for breaks in the line or water running elsewhere which could drain pressure. If you have pop up models, check for water coming out around the guide seal below the sprinkler head. This is a pressure activated seal. if pressure is insufficient, water will leak around this seal causing the unit to stall and pop up only part way. If the unit is new or others on the line have same problem, it is probably related to pressure. If the unit is older, clean or replace the guide nut seal if necessary.

For more troubleshooting, try switching with another sprinkler closer to water source. If it works, then pressure could be the problem. If the sprinkler stopped working within a month or two of installation, the system may not have been designed to accommodate the normal operating pressure of the type of sprinklers installed. If metal sprinklers are being used, try switching to plastic. If plastic sprinklers are being used, try a lower gallonage variety.

Or, there may be debris in the system. Remove sprinkler and check for debris in nozzle, swivel bearing, and inlet. Sometimes, a wire pushed gently into the nozzle will loosen debris so it can be rinsed out. Do not drill or alter nozzles as this may permanently hinder the sprinkler performance. Metal models only: If sand is caught in vane inside of nozzle, it will need to be removed. Loosen nozzle with wrench and unscrew. Thoroughly wash sprinkler to remove dirt and oil. A vinegar and water solution will help remove water deposits.

And, finally, the arm spring tension may need increasing. Metal models: Unhook spring
from arm with needle-nosed pliers. Bend slightly to shorten and re-hook.
Plastic Models: Unhook spring from arm with needle-nosed pliers, re-hook to
next adjoining protrusion on arm.

Hope this information is helpful!

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