July 5, 2023
Low water pressure is one of the sneakiest irrigation problems because the symptom — underperforming coverage — can look identical to broken heads, bad programming, or the wrong head type. Before replacing heads or adding zones, it’s worth making sure the pressure problem is actually about pressure. Here are the most common causes of low sprinkler pressure, ordered from most to least common.
An underground pipe break is the most common cause of sudden, significant pressure loss in a zone that was previously performing well. When a lateral line cracks — from ground movement, freeze damage, root intrusion, or age — water escapes underground before it reaches the heads. The heads pop up but deliver a weak, short-range spray.
A valve that isn’t fully sealing can bleed water between cycles or can fail to fully open when activated — either of which reduces effective pressure in the zone.
This is a design problem rather than a failure. Every zone has a maximum flow capacity based on the pipe diameter, valve size, and available supply pressure.
Many irrigation systems include a pressure regulator — a device that reduces incoming city water pressure (typically 60–80 PSI) to a level suitable for the irrigation system (typically 30–45 PSI). When the regulator fails, pressure may be too low across the entire system.
Most irrigation systems include a filter or strainer at the point of connection to catch debris before it reaches valves and heads. A clogged filter restricts flow and reduces pressure across all zones.
Occasionally the cause isn’t in your system at all — it’s lower supply pressure from the municipal water system. This can be temporary (during high demand) or longer-term (when system improvements change supply zones).
Heads with clogged nozzles can appear to be a pressure problem — the head pops up but delivers a weak, irregular spray. Cleaning or replacing the nozzle usually solves it.