Irrigation and drip system leak detection

Outdoor water is where a Valley property loses the most and notices the least. According to City of Phoenix Water Services, most of the water a Valley home uses goes outdoors — which makes an outdoor leak both the easiest one to miss and the one it hurts most to leave alone. There is no ceiling under a yard and no damp wall to warn you.

What it looks like in a desert yard

• One patch of gravel or granite that stays dark between irrigation runs.
• A green stripe, or one plant doing far better than its neighbours for no reason.
• Standing water in a valve box, or a box that is always damp inside.
• Emitters at the end of a drip run doing nothing while the near ones run hard.
• Algae or salt crust on a wall or kerb where water keeps arriving.
• A bill that climbed in a month when nobody changed the timer.

Flood irrigation: past the SRP gate, the pipe is yours

If your lot is flood irrigated, this is the single most useful thing to understand. Salt River Project’s responsibility ends at its delivery gate. Once a zanjero opens that gate, the water travels to your property through ditches, channels and pipelines that are owned, operated and maintained by the homeowners themselves — who are also responsible for keeping all of that water on their own property.

So the gates, valves, standpipes and buried laterals are private pipe. When one of them is losing water, it is not a call to the utility. Flood irrigation runs through Arcadia, the Biltmore area, parts of Tempe and Mesa, and much of Laveen — where, on the U.S. Census Bureau’s figures, the median home was built in 2006, so newer houses sit on much older irrigation infrastructure.

Source: U.S. Census Bureau, American Community Survey 5-year estimates (2023).

Where systems fail here

Above-grade poly and PVC

Sun destroys unprotected polyethylene drip tubing and exposed PVC risers. The failure is usually a split along the top face of the pipe, and it is often visible once you know to look up-sun rather than down.

Valves and manifolds

A solenoid valve that does not seat fully leaks continuously into the zone downstream of it. That is the sneaky one: the system is “off” and still using water, day and night, and nothing above ground moves.

The pressurised mainline

The line from the point of connection to the valves stays under pressure all the time, so a break in it runs around the clock rather than for the ten minutes a zone is on. A mainline leak is the usual explanation when a bill jumps sharply.

Movement and roots

Monsoon wetting and drying moves the ground, and a rigid fitting shears where it is held between two things that move differently — a riser against a footing, a lateral crossing a trench.

How an irrigation leak is found

Shut the irrigation at its isolation valve and read the meter: if the meter stops, the loss is downstream of that valve and the whole search is now in the yard. Then the system is pressurised in sections — mainline first with all zones off, then zone by zone — with a gauge, so each section proves itself. Where the mainline is the one that fails, acoustic listening and line tracing put it on the ground.

The honest limit: a drip zone runs at low pressure and makes almost no noise, so listening rarely finds a drip leak. Those are found by running the zone and reading the yard — where the water actually surfaces, where the pressure falls off, which emitters starve. And a valve that leaks only when the zone downstream is called will not show on a static meter test at all, which is why we run the system rather than only watch it.

After it is found

Most irrigation repairs are small and above ground once the location is certain — see leak repair. Buried mainline work is a dig, which is exactly why the locating comes first; see underground leak detection.

When it is not an irrigation leak

A sprinkler head aimed at a wall, a timer somebody reprogrammed, an air-conditioning condensate line discharging into a planter, a neighbour’s flood irrigation arriving over the property line, or a pool whose auto-fill is doing the work. We rule those out before digging anything.