Understanding Low Head Drainage

The most common reason a sprinkler head leaks after the system shuts off is low head drainage. This occurs when residual water in the lateral piping drains out through the lowest sprinkler head in that specific zone. Because water naturally flows downhill, even a slight elevation change in your yard can cause the lowest head to weep water until the pipes are completely empty.[1][1][2]

Low head drainage is generally a temporary issue that resolves once the water has drained from the line. While it may look like a leak, it is actually a normal function of gravity acting on the remaining water. To prevent this, homeowners can install check valves, which are designed to hold back the residual water and stop it from draining out of the lowest heads.[1][1][2]

Identifying a Weeping Valve

If the sprinkler head continues to leak continuously and does not stop after a few hours, the problem is likely a weeping valve rather than low head drainage. A weeping valve occurs when the zone valve fails to close completely, allowing water from the main line to seep through. The most frequent cause of a weeping valve is debris, such as dirt or small rocks, obstructing the valve's diaphragm and preventing a watertight seal.[1][1][3][1][2]

Unlike low head drainage, a weeping valve will not be fixed by installing a check valve at the sprinkler head. To resolve a weeping valve, the valve itself must be disassembled, and all parts should be rinsed with clean water to remove any debris. If the diaphragm is damaged or worn out, it will need to be replaced to restore proper function.[1][1][2][1]

When to Call a Phoenix Professional

If you have cleaned the valve and the leak persists, or if you are uncomfortable disassembling irrigation components, it is time to call an irrigation professional in the Phoenix area. A specialist can accurately diagnose whether the issue is a damaged valve diaphragm, a worn seal, or a problem with the system's pressure.[1][3]

Professional irrigation technicians have the tools and expertise to replace faulty valves or install the correct check valves for your system's specific elevation changes. Addressing these leaks promptly not only saves water but also prevents potential damage to your landscape and hardscaping caused by constant pooling.[1][2][3]