Overall Low Pressure (All Zones)
If every zone has low pressure, the problem is upstream of the valves — check the water supply, backflow preventer, master valve, or main line for restrictions.
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Symptoms
- All sprinkler heads have weak spray or short throw distance
- Rotors barely turn
- Pressure is lower than it used to be system-wide
Diagnosis
Something is restricting flow before water reaches the zone valves: partially closed supply valve, clogged filter/backflow, or a main line leak draining pressure.
Step-by-Step Repair
- 1
Check the main irrigation shut-off valve — make sure it's fully open.
- 2
Check the backflow preventer for partial clogs or test cock valves that aren't fully open.
- 3
If you have a master valve, inspect it (see Valve Won't Open guide) — a partially stuck master valve restricts all zones.
- 4
Check for a main line leak that could be diverting water underground.
- 5
Install a pressure gauge at the point of connection to measure static and dynamic pressure. Municipal supply should be 40-80 PSI.
- 6
If your municipal water pressure has dropped, contact your water provider — it may be a supply issue.
Parts Needed
- •Backflow Preventer × 1 — If existing one is restricted or failed
Pro Tips
- Measure pressure at the hose bib closest to the meter. If that's low too, it's a supply issue, not an irrigation issue.
Prevention Tips
- Have your backflow preventer tested annually — it's usually required by code and keeps it functioning properly.
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