Buying a Home With an Automatic Irrigation System? What Buyers Should Check Before Closing (2026)

What should buyers check on an irrigation system before closing? Test every zone for coverage, pressure, and leaks. Verify the backflow preventer is installed and has been tested annually (required by California law). Inspect the controller for programming and wiring condition. Check for broken or misaligned heads, valve box condition, and whether the system is causing water to pool near the foundation.

An automatic irrigation system is one of those home features that looks like a pure positive on the listing sheet. Lush landscaping. Green lawn. Automatic timers. The yard practically waters itself.

Until it doesn't. Or until it does, but in all the wrong places.

During our home inspections in San Diego, irrigation systems are a frequent source of surprises. Buried leaks that have been saturating the soil near the foundation for months. Zones that run but don't actually water the areas they're supposed to cover. Controllers with dead batteries and lost programming. Backflow preventers that haven't been tested since the system was installed. And heads spraying directly against the house, feeding moisture into stucco, siding, and crawl space areas where it has no business being.

This guide covers what we check during an irrigation inspection, what the common defects look like, what they cost to fix, and why the irrigation system deserves real attention during the home buying process.

Why Irrigation Systems Matter During a Home Inspection

An irrigation system isn't just a landscaping feature. It's a plumbing system buried underground that connects to the home's potable water supply, operates under pressure, and distributes water across the entire property. When it works properly, it maintains the landscaping. When it doesn't, it can cause foundation damage from soil saturation, mold conditions from moisture intrusion, wasted water and inflated utility bills, and backflow contamination of the drinking water supply.

In San Diego, where water costs are high and the combination of expansive clay soils and drought-wet cycling creates real foundation risks, an irrigation system that's overwatering one side of the house or leaking underground near the foundation isn't just an annoyance. It's a structural liability.

What We Check During an Irrigation Inspection

Controller and Programming

The irrigation controller (the "brain" of the system) is usually mounted in the garage or on an exterior wall. We check the controller for power, display function, battery backup, and programming. A controller with a dead battery loses its programming during a power outage, which means zones may not run on schedule or may run at default settings that don't match the property's needs.

We also note the number of zones programmed and whether the schedule appears reasonable for San Diego's climate and water restrictions. Overwatering is as much of a problem as underwatering when the excess moisture ends up against the foundation.

Zone-by-Zone Testing

We run each zone individually and walk the property while it's running. For each zone, we check whether the valve opens and the zone activates, whether the heads pop up, spray, and rotate as designed, whether the coverage pattern reaches the intended area without significant gaps or overspray, whether any heads are broken, tilted, sunken, or blocked, whether water is pooling in unintended areas, and whether any heads are spraying against the house, fence, or hardscape.

This is where most irrigation defects become visible. A zone that runs but delivers water to the wrong places (or not enough water to the right places) is functionally failed even though the controller shows it as "active."

Backflow Preventer

The City of San Diego requires backflow prevention on all irrigation systems connected to the public water supply, per California Plumbing Code and California Code of Regulations Title 17. The backflow preventer stops irrigation water (which may contain fertilizers, pesticides, and soil contaminants) from flowing back into the potable water system.

We check for the presence of a backflow preventer, its type (reduced pressure assembly, pressure vacuum breaker, or atmospheric vacuum breaker), its physical condition, and whether it has a current annual test certification tag. California requires annual testing of backflow preventers by a certified tester, regardless of property occupancy. A missing test tag doesn't mean the device is failed, but it means compliance hasn't been documented.

Valve Boxes and Manifold

We check accessible valve boxes for standing water (which can indicate a slow leak at the valve), valve condition, wire connections, and box integrity. Cracked valve boxes, corroded wiring, and submerged valves are common findings in older systems.

Visible Pipe and Connection Condition

While most irrigation piping is underground and not accessible during a standard inspection, we check visible connections at the backflow preventer, the manifold, the controller wiring, and any exposed pipe runs. We also look for evidence of underground leaks: unexplained wet spots in the yard, sinkholes or depressions over pipe runs, and areas of unusually lush growth in otherwise dry landscaping.

Common Irrigation System Defects

Defect	How Common	Typical Repair Cost
Broken or tilted sprinkler heads	Very common	$5 to $20 per head (DIY) or $50 to $100 per head (professional)
Misaligned heads spraying against the house	Very common	$0 (adjustment) to $50 (head replacement and repositioning)
Zone not activating (valve failure)	Common	$75 to $200 per valve (replacement)
Controller malfunction or dead battery	Common	$20 (battery) to $150 to $400 (controller replacement)
Underground pipe leak	Moderate	$150 to $500 per repair (depends on location and depth)
Missing or non-functional backflow preventer	Moderate	$200 to $600 (installation or replacement) plus annual testing fee
Wiring damage (cut, corroded, or shorted)	Moderate	$100 to $300 (repair)
Overspray causing foundation moisture	Common but often unnoticed	$0 to $200 (head adjustment or replacement) but the moisture damage it caused can cost thousands
Clogged heads or filters	Common	$0 to $50 (cleaning or replacement)
System not winterized (freeze damage)	Less common in San Diego but occurs in inland/mountain areas	$200 to $1,000+ depending on extent

Costs are estimates for the San Diego market as of late 2026.

Irrigation and Foundation Risk: The Connection Buyers Miss

This is the part of the irrigation inspection that connects to the rest of the home inspection.

In San Diego, where much of the metropolitan area sits on expansive clay soils, the moisture content of the soil around the foundation directly affects foundation stability. Too much water on one side of the house causes the clay to swell, pushing against the foundation. When the soil dries, it contracts, creating voids.

An irrigation system that oversprays against the house, leaks underground near the foundation, or creates pooling at the base of exterior walls is feeding this cycle. The homeowner may not notice because the irrigation runs at 5 AM. The landscaping looks great. But underneath the surface, the soil is saturated on the irrigated side and dry on the non-irrigated side, creating the differential moisture conditions that drive foundation settlement.

During our inspections, we look for this connection. When we find irrigation heads spraying against the foundation, pooling near the house, or underground leaks near the perimeter, we flag it as both an irrigation defect and a potential foundation concern.

What the Irrigation Inspection Report Should Tell You

A useful irrigation inspection report gives you specific, actionable information for each zone, including which zones work, which don't, what's broken, and where the overspray or pooling is occurring. It should also note the backflow preventer condition and testing status, the controller condition and programming, any visible leaks or signs of underground leaks, and the relationship between the irrigation system and the foundation or structure.

Our inspection reports include photos of every deficient component, the zone affected, and the recommended repair. This gives you what you need to get contractor estimates and negotiate with the seller.

How 360 Home Inspection Evaluates Irrigation Systems

We test every accessible zone of the irrigation system during our standard home inspection when the system is operational and the water is on. We walk the property during each zone run, document deficiencies, and evaluate the system's impact on the home's structural components, particularly foundation moisture and drainage.

When we find conditions that suggest the irrigation system is contributing to moisture problems around the foundation, we connect those findings to the broader drainage and foundation assessment in our report. For the full scope of what we inspect, see our buyer's guide.

Schedule your inspection or call (858) 707-7066.

Frequently Asked Questions

Q: Does a home inspection include the irrigation system?

Most comprehensive home inspections include a functional test of the irrigation system when the system is accessible and the water is turned on. We test each zone for activation, coverage, leaks, and head condition. A standard home inspection does not include an underground pipe pressure test or irrigation design evaluation, which would require a specialist.

Q: What should I check on an irrigation system before buying a house?

Run every zone and walk the yard while each is running. Check for broken or misaligned heads, areas of overspray against the house, pooling near the foundation, and zones that don't activate. Verify the backflow preventer is present, in good condition, and has a current test tag. Check the controller for proper programming and battery backup.

Q: Is a backflow preventer required on an irrigation system in San Diego?

Yes. The City of San Diego, per California Plumbing Code and Code of Regulations Title 17, requires backflow prevention on all irrigation systems connected to the public water supply. Annual testing by a certified tester is also required. Irrigation systems are specifically listed as cross-connection hazards that require backflow protection.

Q: How much does it cost to repair an irrigation system?

Common repairs range from $5 to $20 per broken sprinkler head (DIY) to $75 to $200 for valve replacement and $150 to $500 for underground pipe leak repair. A full controller replacement costs $150 to $400. Backflow preventer installation or replacement costs $200 to $600. The total depends on how many defects the system has and the complexity of the repairs.

Q: Can an irrigation system cause foundation damage?

Yes. An irrigation system that oversprays against the house, leaks near the foundation, or creates pooling at the base of exterior walls saturates the soil around the foundation. In San Diego's expansive clay soils, this moisture drives the swelling and contraction cycle that causes differential foundation settlement. The irrigation system is one of the most common and most overlooked sources of excess foundation moisture.

Q: What is a backflow preventer and why does it matter?

A backflow preventer is a device installed on the irrigation system's water supply line that prevents irrigation water (which may contain fertilizers, pesticides, and soil contaminants) from flowing back into the potable water system. California law requires backflow prevention on all irrigation connections and mandates annual testing to verify the device is functioning.

Q: How do I know if my irrigation system has an underground leak?

Signs of an underground irrigation leak include unexplained wet spots or muddy areas in the yard when the system isn't running, sinkholes or depressions over pipe runs, areas of unusually lush growth surrounded by dry landscaping, and a water bill that's higher than expected. A professional leak detection service can pinpoint the location.

Q: Should I negotiate irrigation repairs with the seller?

Minor irrigation defects (a few broken heads, controller battery) are typically not worth negotiating. Significant defects (multiple failed zones, underground leaks, missing backflow preventer, system causing foundation moisture) are worth including in a repair request. The repair costs are usually moderate, but the consequences of unaddressed leaks and overspray can be expensive.

Q: What happens if the irrigation system isn't working during the inspection?

If the system is turned off (winterized, water shut off, or controller disconnected), we note that the irrigation system was not operational and could not be tested. We recommend that the buyer request the seller activate the system for a follow-up test before the inspection contingency expires. An untested irrigation system is an unknown.

Q: How long do irrigation systems last?

Irrigation system lifespan depends on the components. Controllers last 10 to 15 years. Valves last 10 to 20 years. PVC pipe can last 25 to 40 years or more. Sprinkler heads last 5 to 15 years depending on type and exposure. Backflow preventers last 10 to 25 years with annual maintenance. The system as a whole requires ongoing maintenance rather than a single replacement event.

Final Thoughts

An automatic irrigation system is a convenience until it becomes a problem. The system that keeps the landscaping green can also be the system that saturates the foundation, wastes water, and creates moisture conditions that cost thousands to remediate.

Test every zone. Walk the yard while the water's running. Check the backflow preventer. Look at where the water goes, not just whether it flows. And if you see water pooling against the house, that's not the irrigation doing its job. That's the irrigation creating your next repair bill.

Irrigation repair costs and backflow prevention requirements in this article reflect San Diego market conditions and California state regulations as of 2026. Costs, regulations, and system specifications vary by property, contractor, and jurisdiction. Consult licensed irrigation professionals and the City of San Diego Public Utilities for compliance questions.