Why Is My Irrigation System Losing Pressure?
UK Flow Centre problem guide
Find out whether the problem is supply, restriction, leak or demand
Pressure loss is not one fault. Start by identifying where it happens: everywhere, in one zone or only at the far end.
1. Read where the pressure is lost
- Every zone is weak: investigate the water source, pump duty, supply pressure, main filter and any restriction before looking at individual sprinklers.
- Only one zone is weak: look at that valve, its filter or regulator, zone pipework, a local leak, or too many outlets running together.
- The first heads work but the far end does not: pipe size, run length, elevation change or excessive flow demand are likely contributors.
- Pressure starts normally then drops: check a falling tank or borehole level, a blocked filter, pump control or a leak that becomes apparent under pressure.
2. Work through the system in order
Water source and pump
Confirm the pump or incoming supply can meet the required flow at the required working pressure. Maximum flow and maximum head figures do not describe the same operating point. A pump that is suitable for one sprinkler or outlet may not suit several operating together.
Filters, valves and controls
Inspect filters and strainers for restriction. Check that isolation valves are fully open and that control valves, pressure regulators and pump controls are set and operating as intended. A pressure regulator limits downstream pressure; it cannot correct an undersized pump, blocked filter or badly sized main.
Pipework and leakage
Pipe friction rises with flow and distance. Small pipe, long runs, unnecessary fittings and sudden reductions can consume useful pressure. Visible wet ground, a meter moving when no water should be used, or a pump cycling unexpectedly can point to a leak, but underground faults may need formal investigation.
3. Take readings that separate pressure from flow
- Static pressure: record pressure with no zone or outlet running.
- Dynamic pressure: record pressure while the affected zone is operating.
- Compare locations: where safe test points exist, compare the source, after the main filter and the affected zone.
- Record flow demand: pressure without the corresponding flow and number of operating outlets can be misleading.
Start at the source, pump or incoming supply, then check the main filter and shared mainline.
Investigate that filter, valve, regulator or restriction before changing the pump.
Check its valve, local pipework, leak, elevation change and operating outlet demand.
Manufacturer example: Hunter's Accu-Sync pressure-testing guidance measures running pressure at the farthest head for that specific valve arrangement. Use the procedure and test equipment intended for your installed components.
Make the readings useful to the person checking the fault
- Give each test point a location or drawing reference and note its height.
- Record the gauge range, units and zero condition, plus the meter or method used for flow.
- Record which outlets are running, pump/control state and source or tank level.
- Note whether the reading is steady or changes during the cycle, and when it was taken.
- Retain the original alarm message and recent changes before making adjustments.
A pressure difference between points can include elevation as well as component losses. Use a common height datum and paired flow readings before attributing the whole difference to a blocked component. Rain Bird’s water-supply explanation distinguishes available flow, friction losses, elevation and remaining working pressure.
If there is repeated tripping, electrical damage, uncontrolled pressure or flooding, stop and obtain competent help. Do not repeatedly reset equipment or open live pipework to collect a reading.
4. What may help after the cause is identified
- Blocked filtration: clean, repair or resize the filtration arrangement for the expected flow and water quality.
- Excessive zone demand: reduce the number of outlets operating together or redesign the zone.
- Pipework restriction: remove unsuitable bottlenecks and review the main size, run length and fittings.
- Leak or damaged valve: locate and repair the fault before changing the pump.
- Inadequate pump duty: select a pump from its curve against the actual installation duty.
Use these examples to identify the type of component you may need. Match the product type to the proven fault, then check the exact technical data for the installation.
A new filter or pump will not cure an unidentified leak, closed valve or undersized pipe.
Before you ask for help
Send the pump model, pipe sizes, lengths and elevation changes, number and type of outlets running, pressure readings if available, water source and a sketch of the system. This is enough to start separating a design issue from a fault.
Quick pressure-loss questions
Is the pump always the cause of low pressure?
No. The cause may be the water supply, a blocked filter or partly closed valve, restricted pipework, leakage, or too many outlets operating together.
Can a pressure regulator increase downstream pressure?
No. A regulator limits pressure; it cannot correct an undersized pump, blocked filter or badly sized main.
Should I fit a larger pump first?
Not before identifying the cause. More pump can worsen leaks, water hammer and unsuitable pipework. Establish the required flow, pressure, pipe size and control arrangement first.
Read the pump buying guide Shop pumps Shop filtration Shop irrigation pipe
Planning for autumn or winter? Record pressure and flow symptoms before shutdown, then use the seasonal system checklist.
Technical guidance from UK Flow Centre, operated by JK Irrigation Ltd. Explore all guides in the Technical Hub.
