One dead zone with the rest of the system healthy is almost never a pump or a city supply problem. It is a station circuit: solenoid, field wire, or that one controller output.
In Alamo Ranch we find cut commons after fence jobs, nicked wire under new beds, and solenoids that open electrically but pass no water because the diaphragm is stuck.
The three-minute split
At the controller we jump the station terminal to common. If the valve clicks in the box, the controller is fine and the problem is hydraulic. If nothing happens, we meter the solenoid (typical coil is around 20–60 ohms) and chase the wire with a tracer.
West growth corridor with new construction punch lists. Buried boxes under mulch are common on this route — we locate them before we dig.
What we replace
A shorted coil gets a matched solenoid. A crushed wire gets a waterproof splice, not electrical tape in a wet box. A valve that hums but will not open usually needs a diaphragm rebuild — see Valve Repair & Replacement.
DIY that is safe
You can confirm the station is programmed, not on a rain delay, and that the backflow is open. Do not pull the solenoid with the system pressurized unless you know how to shut the zone down. A surprise geyser in {city} clay is a mess.
San Antonio conditions that change the repair
San Antonio irrigation lives with limestone, caliche, pockets of black clay, Edwards Aquifer hard water, and long hot summers. Those conditions scale nozzles, walk heads out of grade, and punish weak valves.
Alamo Ranch is in Bexar County. West growth corridor with new construction punch lists. That is why a generic statewide watering guide fails here — the soil does not take water the same way, and the mineral load is different.
Twice-yearly checkups (spring startup and a pre-freeze look at the backflow) catch buried heads and weak solenoids before they brown a lawn in July.
Related services
Our Valve Repair & Replacement page covers how we handle this on a live system. If you are in Alamo Ranch, start with sprinkler repair in Alamo Ranch.
– Leak Detection & Line Repair
– Smart Controller Installation
Browse the full services list or all San Antonio service areas.
Quick question
Is a humming valve always a new valve? No. Humming means the solenoid is powered. The diaphragm or a clogged port is often the actual failure.
When to call
Call Sprinkler Repair Tech if a zone will not shut off, water is pooling toward a foundation, or half the yard is offline in Alamo Ranch heat. Those are same-week jobs. Tune-ups and audits book on the next route day.
We are a call-first repair company. Technicians carry solenoids, diaphragms, spray bodies, rotors, and nozzle trees so most Alamo Ranch repairs finish in one visit. You get a plain-language explanation of what failed and how to water the soil you actually have.
Photograph the controller program before any upgrade. Label the valve box once we find it. Those two habits prevent a lot of repeat Alamo Ranch calls after the next landscaper or freeze.