Irrigation · Service

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.

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In short

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.

Triggers

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

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The job

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 for: A 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 for: A 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 for: A 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 for: A 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 for: No 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.

Money

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 →

Straight answer

When irrigation leak detection is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

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.

Before you sign

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.

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Local pros

Irrigation Leak Detection near you

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Related work

Often done at the same time

Sprinkler Repair

Once the fault is located and visible

Irrigation Audit

When water use is high but nothing is leaking

Irrigation System Redesign

When leaks keep recurring in old pipe

Plumbing Leak Detection

For losses inside or under the house

All irrigation services →

FAQ

Irrigation Leak Detection — questions people ask

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How do I tell whether the leak is on my irrigation system or in the house?

Shut off the valve that isolates the irrigation system from the house supply and watch the meter. If the meter stops, the loss is on the irrigation side; if it keeps moving, it is indoors or on the house side of the plumbing. Do this before anything else — it costs nothing and it decides which trade you call.

Can an irrigation leak run without ever showing on the surface?

Routinely, yes. Water follows the path of least resistance underground: along the pipe trench, into gravel, along a footing drain, or down into permeable subsoil. Sandy and well-drained soils in particular can absorb a substantial continuous leak with no visible sign at all, which is why a bill jump is often the first and only symptom.

Is a leaking valve the same as a leaking pipe?

No, and they are distinguished differently. A valve that fails to seat lets water past into a lateral, so you get a zone that weeps or a head that trickles constantly. A mainline pipe leak loses water into the ground with no zone running at all. The meter test plus a walk of the zones separates the two before anyone digs.

How accurate is acoustic leak detection on irrigation pipe?

Less accurate than on metal water mains, and it is worth knowing that going in. Plastic pipe damps the sound a leak makes, and shallow burial in soft soil damps it further. In practice good technicians combine route tracing, section isolation and pressure decay with acoustics rather than relying on listening alone, and they describe a search area rather than promising a point.

Should I just shut the system off until it is repaired?

For a mainline leak, yes — close the isolation valve and the loss stops immediately, which is worth doing the moment you suspect one rather than waiting for an appointment. For a lateral leak, simply skipping that zone stops the loss while the rest of the system keeps running. Either way, do not leave a confirmed continuous leak running through a billing cycle.