Finding a Mainline Leak When the Meter Spins But No Zones Run

Linda's 16-zone system ran fine in May, but now no water reaches any zone. The water meter spins rapidly with no other water use, indicating a significant leak between the valves and the stations. She asks about leak detection tools like "divining rods."

First: Rule Out Simple Valve Issues

Tony's first step is practical: "Check all the control valves. Look for open bleed screws and solenoids left partially open. If there is more than 1 valve left open at once, the water will run to both (or all) open valves which will not be enough to run multiple zones yet still make your meter spin." This is a common oversight after spring startup or maintenance.

If Valves Are Confirmed Closed: Mainline Leak

If no valves are open manually or electrically, the leak is on the mainline. Tony advises shutting off the water source immediately. Since pipes are typically buried only 8-12 inches deep, the water will surface relatively quickly. "Follow and walk the route of the main line with the water running and it will eventually turn up in the form of a soft spongy area above the problem area."

No Magic Tools Needed

While electronic leak detectors exist (acoustic listening devices, ground-penetrating radar), for a residential mainline leak this size, the "walk the line" method is often fastest and requires no special equipment. The key is confirming the valves are truly closed first—otherwise you're chasing flow that's supposed to be there.