Winterization & Blow-Outs
One hard freeze is all it takes
to crack what you spent thousands building.
North Idaho winters are not forgiving to irrigation systems left with residual water in poly laterals, brass backflow assemblies, and valve bodies. A January that dips to 8°F — well within normal range for Post Falls and Rathdrum — will find every water-filled fitting in your system. Poly pipe cracks at the elbow. Valve bodies split at the diaphragm seat. Backflow assembly chambers freeze solid.
LP's winterization service uses commercial rotary screw compressors producing real volume — not underpowered consumer units that leave water in the laterals just beyond the head. We purge every zone, drain every valve, properly position every backflow assembly, and document everything before we leave. Your system wakes up in April the same way it went to sleep in September.
Water expands when it freezes.
Your fittings don't.
Prevents Freeze-Crack Damage to Poly Pipe and Fittings
Water expands approximately 9% when it freezes. Poly lateral line, PVC mainline, and brass fittings that hold residual water through a Kootenai County winter — where January lows regularly reach 10–15°F — will crack. A single cracked lateral segment that LP would have cleared for under $150 at winterization can cost $400–$900 to locate, excavate, and repair in spring.
Protects Ball Valves and Diaphragm Valves
The shutoff ball valves on your backflow assembly and the diaphragm valves controlling each zone are the most expensive individual components in the system. Brass ball valves that freeze crack at the body, requiring full assembly replacement. Diaphragm valves with residual water in the pilot chamber can split the valve body or destroy the diaphragm seat, turning a $12 service part into a $65–$120 valve replacement.
Insurance Against Early October Cold Snaps
North Idaho's first hard freeze varies considerably by year — the average first freeze in Post Falls is around October 15, but one-in-five years sees a freeze event before October 1. Homeowners who schedule winterization in early October are protected. Those who wait until "it stays cold" take a meaningful risk every year. LP runs blow-outs beginning in mid-September, and schedules fill quickly.
Documented Record for Spring Startup
LP's written zone map and shutdown confirmation eliminates the guesswork at spring startup — we know which valve controls which zone, what pressure each zone ran at in the fall, and what issues were noted. For homeowners who sell their property, that documentation transfers as a system record to the new owner, a real asset during a North Idaho real estate transaction.
Volume, sequence, and documentation —
not a single-pass guess.
Commercial Compressor Sizing
The most common mistake in irrigation blow-outs is an undersized compressor. Consumer-grade units producing 5–12 CFM cannot move enough volume through lateral lines to fully purge residual water — they clear the head itself while leaving standing water 12–18 inches back in the lateral, exactly where freeze damage occurs. LP uses commercial 2-stage rotary screw compressors producing a minimum of 20 CFM at 50 PSI, ensuring adequate volume to fully evacuate each zone's lateral lines regardless of pipe diameter.
Zone-by-Zone Purge Sequence
LP runs every zone through a minimum of 2–3 passes, not a single blast. The first pass clears bulk water from the mainline out to the heads. The second pass draws residual moisture from the lateral lines and fittings. For zones with significant elevation change or long lateral runs — common on sloped North Idaho lots — a third pass ensures the low points are fully evacuated. Pressure limits are strictly observed: spray heads at 50 PSI max, rotors at 50 PSI max, drip zones at 45 PSI, to prevent seal and diaphragm damage.
Backflow Assembly Winterization
RPZ and double-check backflow assemblies have internal chambers and test ports that hold water after a standard blow-out if not properly drained. LP drains backflow assemblies fully, repositions the two shutoff ball valves to the 45-degree intermediate position (which prevents vacuum-lock during spring fill), and leaves the test cocks slightly open — the industry-standard positioning that prevents trapped water from expanding in the brass body during a freeze.
Valve Box & Manifold Protection
Valve bodies and manifold assemblies sitting below grade in plastic valve boxes collect residual water in the solenoid ports, pilot tubing, and diaphragm chambers. LP manually drains valve bodies after the zone blow-out cycle, confirms pilot ports are clear of standing water, and inspects valve box covers for cracks or missing lids that would expose the manifold to full freeze penetration during January cold snaps.
Controller Shutdown
Simply setting an irrigation controller to "Off" doesn't always protect it from a power outage or a start signal from a malfunctioning sensor. LP sets every controller to "Rain Mode" rather than full off — this preserves programs and zone runtimes for spring startup while preventing any zone from firing, even if a sensor glitch or power restoration sends an errant activation signal. Battery backup modules are inspected and battery condition noted.
Post-Blowout Documentation
When LP finishes a winterization, we leave the homeowner with a written zone map showing each controller station, its corresponding valve location, head count, and pipe size, along with a dated shutdown confirmation noting compressor CFM used, pressure observed per zone, and any damage or concerns identified during the blow-out. That document travels to our file too — so when you call for spring startup, we're not starting from scratch.
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