A drip irrigation system delivers water directly to plant root zones and requires a specific, relatively low operating pressure to function correctly. The ideal pressure range for most systems is between 10 and 30 pounds per square inch (PSI), often performing optimally around 25 PSI. When pressure drops below this range, emitter performance becomes inconsistent, leading to uneven watering. This inconsistency reduces the system’s water-saving efficiency, a primary benefit of drip irrigation.
Pinpointing the Cause of Low Pressure
Before attempting repairs, accurately diagnose whether the problem is low pressure or low flow, and where the loss is occurring. Pressure is the force of water (PSI), while flow is the volume of water over time (GPM or GPH).
The most effective diagnostic tool is a pressure gauge. Use it to measure the static pressure before the system’s head assembly and the dynamic pressure at the end of a lateral line. Static pressure, measured when no water is flowing, indicates the water source’s potential. Dynamic pressure, measured while the system is running, reveals the pressure loss due to friction and components within the lines. If the pressure is acceptable at the source but low at the end of the line, the issue lies within the system components or layout.
Also check the pressure reducer, which is designed to lower and stabilize the incoming water pressure to the ideal operating range. These devices can sometimes fail or be set incorrectly, so verifying the regulator’s output pressure is necessary. Systematically checking pressure at different points helps isolate the problem to the water source, the head assembly, or the distribution network.
Enhancing Pressure at the Water Source
If diagnostics confirm the static pressure from the main water source is consistently below the required 10 to 30 PSI, the problem must be addressed at the beginning of the system. First, ensure all shut-off valves, including the main valve and any hose bibs feeding the system, are completely open. A partially closed valve significantly restricts flow and limits the available pressure for the entire system.
If municipal or well pressure is inherently too low, a booster pump is the most effective solution for increasing water pressure. These pumps are installed on the supply line to increase the pressure flowing into the irrigation system. When selecting a pump, match its performance curve to the system’s total flow requirement (GPM or GPH) and the desired pressure (PSI).
When sizing the pump, consider the total head, which is the pressure needed to overcome friction loss and elevation changes. A properly sized booster pump ensures the system operates at a consistent, regulated pressure. Also, inspect components immediately following the main connection, such as backflow preventers or older meters, as these can create restrictions that limit flow and pressure.
Maintaining and Improving System Components
The majority of pressure issues within a drip system are caused by blockages and friction loss within the components themselves. The filtration system, whether a mesh or disc filter, is a common point of pressure drop because it traps sediment and debris. Regularly cleaning the filter by removing the cartridge and rinsing it is essential maintenance. If the filter is severely clogged, a short soak in a mild bleach solution can help dissolve organic buildup like algae.
Leaks in the mainline, sub-main, or lateral lines are a significant cause of pressure reduction. Even small punctures or loose connections allow water to escape, reducing the volume available for the emitters. Identify leaks by visually inspecting the tubing for wet spots or listening for hissing sounds when the system is running. Repairing leaks with goof plugs or couplers restores the system’s integrity and recovers lost pressure.
Regularly flushing the lines removes fine sediment and debris that accumulates inside the tubing. This involves opening the end caps or flush valves at the termination points of the lateral lines and allowing the water to run until it flows clear. This action removes material that contributes to friction loss and emitter clogging, ensuring uniform pressure distribution. Finally, verify the pressure regulator is functioning within its specified range, as a faulty regulator can fail to maintain the target pressure.
Adjusting Layout and Zoning
If maintenance and source-side fixes do not resolve low pressure, a structural redesign of the system’s hydraulics is needed. The length and diameter of the tubing are primary factors in pressure loss due to friction. Shorter lateral lines minimize the distance water travels, which reduces the friction loss that occurs as water moves against the tubing walls.
Increasing the tubing diameter on the main distribution lines is an effective way to mitigate pressure loss, especially in larger systems. Upgrading the main line significantly increases the internal volume, allowing the same amount of water to flow at a lower velocity and with less friction. This change can dramatically improve flow capacity.
For systems that draw too much water for a single run, dividing the overall irrigation area into multiple smaller zones is necessary. Zoning splits the total water demand into smaller, manageable sections that run sequentially. This ensures that each zone receives sufficient pressure and flow, preventing the furthest emitters from being starved of water.