Las Vegas Valley Water District data shows that landscape irrigation accounts for 60-70% of residential water use in our region. When something goes wrong with that irrigation system — and Vegas heat, freeze cycles, and shifting soil mean it eventually does — you can lose enormous amounts of water without ever seeing it on the surface.
How irrigation leaks happen
Five main causes:
1. Cracked mainline supply
The mainline is the buried PVC pipe between your house valve and the irrigation system. It's typically 1-foot deep PVC, often 1-1.5 inches in diameter. Over time, ground movement, freeze cycles, or aging glue joints lead to cracks. A cracked mainline leaks 24/7 — not just when the irrigation runs.
2. Failed zone valve
Zone valves are the solenoid-controlled valves that turn on/off when your controller fires. When one fails OPEN, that zone runs constantly until you notice. Often you don't notice because the actual sprinklers may not be running visibly — water is leaking out of the valve manifold or downstream pipe.
3. Broken sprinkler head
The most visible kind, but easy to miss if it's behind shrubs or only happens during irrigation cycles you don't observe (early morning).
4. Cracked drip lines
Drip irrigation tubing is buried at the surface or 1-2 inches deep. UV exposure, rodents, gardeners, and freeze cycles all damage it. Small leaks here add up — a quarter-inch crack can dump 30 gallons in a 15-minute cycle.
5. Backflow preventer failure
Required by code, the backflow preventer keeps irrigation water from contaminating drinking water. When it fails, water can leak from the device continuously.
The math gets ugly fast
A cracked mainline leaking 1 gallon per minute = 1,440 gallons per day = 43,200 gallons per month. At Vegas rates that's $150-$250 in extra cost EVERY MONTH the leak runs. Customers have come to us with year-old leaks that cost them $2,000-$3,000 cumulatively.
How to spot an irrigation leak
Sign 1: Bill spike without indoor changes
If your bill went up but no one's showering more, no toilets are running, and no one's filled a pool — irrigation is the prime suspect.
Sign 2: Wet patches in the yard
Soggy or unusually green areas, especially when irrigation isn't running, point to underground leaks. Vegas heat means the surface dries fast, so look for these in early morning or after sundown.
Sign 3: Hissing sound near valves
Walk to your zone valve manifold (usually a black box buried in the ground with a green lid). Listen. If you hear hissing or running water when no zones are firing, that's a valve leak.
Sign 4: Different zones running than expected
If you notice sprinklers running when your controller says they shouldn't be, a valve has failed open.
Sign 5: Reduced pressure to some zones
If certain zones suddenly water less area or less effectively, there's likely a leak upstream stealing pressure.
The meter test (essential)
This is the most powerful diagnostic any homeowner can do, and it works for irrigation leaks specifically:
- Make sure no one is using water inside the house.
- Turn off the irrigation controller (no zones running).
- Watch the water meter for 2-3 minutes.
- If the meter is moving — water is being used somewhere. Could be inside, could be irrigation.
- Now shut off the irrigation isolation valve (usually near the house, sometimes in a green box in the yard).
- If the meter STOPS, the leak is in the irrigation system.
- If the meter is STILL moving, the leak is inside the house (slab or fixture).
How we find irrigation leaks
Once we know the leak is in the irrigation system, we narrow it down systematically:
Step 1: Zone isolation
We pressurize each zone individually and watch for pressure drop. The bad zone reveals itself.
Step 2: Acoustic detection
On the bad zone, we walk the route with our ground microphones. We can hear pressurized water escaping underground — same equipment we use for slab leaks.
Step 3: Visual confirmation
We open a small area where the acoustic signal is loudest. The leak is almost always within a foot of where we pinpointed it.
Step 4: Repair
Cracked PVC: cut, replace with new section, glue. Failed valve: remove, replace. Broken sprinkler: replace head. Drip line: splice in new section.
What it costs
- Underground Leak Detection: $295-$495
- Simple sprinkler head repair: $75-$150
- Zone valve replacement: $150-$350
- Mainline crack repair (single spot): $250-$500
- Backflow preventer rebuild/replace: $200-$550
- Full irrigation mainline replacement: $1,200-$2,800
Prevention tips
- Annual irrigation check in spring before peak use season — catches issues before summer water bills
- Winterize the system before freeze season — drain, insulate exposed components
- Check valve manifolds annually for leaks and clean dirt out of valve bodies
- Replace plastic risers with brass or schedule-80 PVC — much more durable
- Smart controllers with weather sensors can reduce overall use and detect anomalies
"I've seen customers' bills triple from a single buried mainline crack. The hardest part is knowing to look — once you know, finding it is the easy part. Our acoustic gear hears it under two feet of dirt." — Matt, owner
Call for an investigation
If you've had a bill spike and your toilets are fine, the irrigation system is the prime suspect. Call (702) 682-1626 — we'll come out, isolate the system, and find the leak. Most jobs done in 1-3 hours.