Irrigation leak detection - the bill found it first
A leak on a pressurised irrigation mainline runs twenty-four hours a day and often never reaches the surface. Locating it precisely is what stops the yard being dug up in five places.
What is irrigation leak detection?
Irrigation leak detection is the work of finding water escaping from buried pipe when there is no obvious break to point at. The critical distinction is whether the leak is on the mainline - the section that stays pressurised at all times, which loses water around the clock - or on a lateral downstream of a valve, which only loses water while that zone runs. A meter reading with the whole system idle answers that question in ten minutes.
Signs you need irrigation leak detection
- Your water bill has jumped with no change in how you use water indoors
- The meter's leak indicator keeps turning with every tap in the house shut off and the controller in the off position
- A patch of lawn stays wet, spongy or unusually green weeks after any watering
- Water surfaces along a line rather than around a point - the classic signature of a pipe seam rather than a head
- You hear water running in the valve box or near the point of connection when nothing is scheduled
- The far heads on one zone have lost throw while the near ones look normal
- Gravel, silt or sinkholes appear along a known pipe route
- The system was recently dug near - fence posts, a new patio, tree planting, edging work
Seeing something not on this list? Browse irrigation problems by symptom →
How irrigation leak detection actually works
Meter test to split mainline from lateral
Everything indoors is shut off and the controller is set to off. If the meter still moves, water is escaping from something permanently pressurised - the mainline, the point of connection, or a valve that is not seating. If it stops, the loss only happens while a zone runs.
Watch forA quote for excavation before this test has been done. It takes minutes, it is free, and it eliminates half the possible locations.
Isolate section by section
The technician closes isolation valves progressively, watching the meter after each, to narrow the loss to a length of pipe rather than a property. Where isolation valves do not exist, the mainline may be capped in stages instead.
Watch forA system with no isolation valves at all. This makes every future repair more expensive, and it is worth adding one or two while the ground is open.
Pressure test the suspect section
The isolated length is charged and then watched with a gauge. A section that holds pressure is clear; one that decays is where the leak is, and the rate of decay gives a rough sense of the size.
Watch forA test run for only a minute or two. Slow leaks - the ones that quietly cost the most over a season - need a longer hold to reveal themselves.
Locate precisely, with a method appropriate to the pipe
Pinpointing may use acoustic listening equipment, a pipe locator to trace the route first, or observation of surface signs. Plastic pipe transmits leak sound far less readily than metal, so tracing the route and correlating with soil conditions often matters more than listening alone.
Watch forA claim of pinpoint accuracy on plastic pipe from listening alone. Honest technicians describe a search area and narrow it; anyone promising a spot within an inch on poly is overselling the physics.
Mark, excavate narrowly, repair and re-test
The location is marked, a small opening is made rather than a trench, the fault is repaired, and the section is re-pressurised and held to confirm the loss has actually stopped.
Watch forNo confirming re-test. Systems with one leak frequently have two - the same freeze event or the same root that caused one usually caused another nearby.
What does irrigation leak detection cost?
Detection is typically billed as a diagnostic visit, with excavation and repair quoted separately once the fault is located. Cost scales with how far the search has to run and what the leak sits under. See the Cost Guide for ranges.
See the full irrigation leak detection cost guide - by material, size and region →
If the number is the problem, here are the ways people pay for it →
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When irrigation leak detection is the wrong call
When saying yes is the wrong move:
- The meter does not move with everything off. Then there is no continuous leak, and paying for detection will confirm that at your expense. Your problem is a zone-level fault - start with repair or an audit instead.
- You can already see it. Water surfacing at a specific head or a valve box you can point to does not need detection equipment. It needs a repair visit, and paying a detection fee first adds a step to a job that has already been diagnosed.
- The loss is indoors. A running toilet flap is the most common cause of an unexplained bill and costs nothing to check. Rule the house out before you assume the yard - a plumbing leak detection service covers the indoor side.
- The system is scheduled for replacement anyway. If the pipe is brittle and multiple leaks have appeared in one season, chasing them individually is an expensive way to delay. Detection costs stack up fast against a redesign.
- You are in the middle of a hard freeze. Pressurising and testing a system in freezing conditions can create new faults. Shut it off at the isolation valve to stop the loss and schedule the work when conditions allow.
- The utility has already told you the leak is on their side. Losses between the main and the meter are the utility's responsibility. Confirm which side of the meter the loss is on before hiring anyone.
What to check when hiring for irrigation leak detection
- Will you do a meter test before quoting anything? It is the cheapest, fastest test available and it determines the entire approach. Anyone who skips it is guessing with your excavator.
- How do you locate on plastic pipe specifically? Most residential irrigation is polyethylene or PVC, both of which are acoustically poor. You want to hear about route tracing and isolation, not just a listening device.
- Is the detection fee separate from the repair, and does it come off? Practice differs widely. Knowing this changes which quote is genuinely cheaper once repair is included.
- What happens if you cannot find it? It happens, particularly with very slow leaks. Agree in advance what you pay for an unsuccessful search and what the next step would be.
- How much of the yard will be opened, and who restores it? The whole point of paying for detection is a small hole instead of a trench. Get the restoration expectation in writing.
- Will you re-pressurise and hold the line after the repair? Your only proof the loss actually stopped - and the way a second, smaller leak gets caught on the same visit.
Irrigation Leak Detection near you
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Sources
Sources last checked
- WaterSense — Outdoor Water UseU.S. Environmental Protection AgencyRetrieved 2026-08-04Federal efficiency labeling and outdoor water-use guidance.
- Occupational Employment and Wages — Construction TradesU.S. Bureau of Labor StatisticsRetrieved 2026-08-04Labor cost context for home-services trades nationally.
Sources for figures and claims on this page.
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