Skipping winterization exposes the entire irrigation infrastructure to a high risk of catastrophic failure. Water left in pipes and components will inevitably freeze, leading to damage that is often hidden underground and discovered only months later. The consequences of this oversight result in a complex and costly series of repairs involving hardware replacement, extensive excavation, and specialized professional services. The expense of a proper “blow out” procedure is minimal compared to the thousands of dollars required to fix a freeze-damaged system in the spring.
The Physics of Freezing Water
The fundamental reason a sprinkler system fails in cold weather lies in the unique molecular structure of water. Unlike most substances that contract as they solidify, water expands when it changes from a liquid to a solid state, increasing its volume by approximately 9%. This expansion is the source of all freeze-related damage.
When water freezes within a rigid, closed pipe section, this volume increase generates immense internal pressure, known as hydrostatic pressure, which can exceed 40,000 pounds per square inch (psi). Since common sprinkler system materials are designed to handle typical operating pressures of 40 to 60 psi, they cannot withstand this enormous internal stress. The pipe or component must yield, resulting in a rupture or crack to relieve the pressure created by the expanding ice.
Failure of Above-Ground System Components
The components situated above ground are the first and most expensive casualties of improper winterization. The most susceptible part is the backflow prevention device (BFP), which is commonly made of brass or plastic and contains sensitive internal mechanisms. If water is trapped inside the BFP body, the expanding ice can crack the brass housing, which typically yields at pressures around 17,000 to 22,000 psi.
Freezing often destroys the internal bonnet and poppet assemblies. A complete failure of the BFP requires immediate replacement, not repair, and necessitates a certified backflow specialist. Replacing a damaged backflow preventer assembly typically costs between $280 and $1,550 for parts and labor, an expense that may also involve regulatory testing and permitting.
Other above-ground elements, such as solenoid valves and sprinkler heads, are also highly vulnerable. Solenoid valves, which control the flow to different zones, can crack at the plastic body or suffer seal failure. Rotary and gear-driven sprinkler heads, with their intricate internal gears, can be completely destroyed when water freezes inside the casing, requiring the replacement of the entire head unit.
Catastrophic Damage to Underground Piping
Damage to the buried components of the system is less visible but often more extensive and labor-intensive to fix. Water trapped in the underground lines, especially at low points, will freeze and exert pressure on the pipe walls.
Although PVC and polyethylene piping possess some flexibility, the force of the ice expansion frequently causes longitudinal splits along the length of the pipe. Critically, the weakest points are the joints and fittings, leading to complete separation or fracturing. This damage is entirely concealed by the soil and lawn throughout the winter.
The true problem emerges in the spring when the system is repressurized and water begins to flow through the hidden cracks. Low water pressure, soggy spots in the lawn, and an unexplained spike in the water bill are the first signs of this underground catastrophe. Locating these leaks requires professional diagnosis and extensive excavation. Repairing a single underground pipe break can cost $150 to $450, with multiple breaks quickly compounding the total expense.