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A Gardening Know How report says turning off a sprinkler system may not remove water left in pipes, valves and sprinkler heads, which can freeze and damage equipment. It describes draining the system or using a controlled, zone-by-zone compressed-air blowout, while warning that incorrect pressure and unsafe handling can cause damage or injury. Local climate and system design affect which method is appropriate.
A Gardening Know How report says homeowners should not assume that shutting off an irrigation system is enough to protect it from a freeze: water can remain in pipes, valves and sprinkler heads and expand as it freezes. The report recommends winterizing before the area’s first hard freeze, using drainage or a carefully controlled blowout where the system and local conditions call for it.
Closing the water supply prevents more water from entering the system, but it does not necessarily clear water already inside. According to the report, residual water may sit in low points in buried pipe, valves and sprinkler casings. As that water freezes, expansion can crack pipes, fittings, valves or sprinkler components, leaving repairs to address when irrigation resumes in spring.
The report describes a blowout as one way to remove remaining water from an in-ground system. It says to shut off the supply, connect an air compressor at the system’s blowout fitting downstream of the backflow preventer, and open one irrigation zone before introducing air. The backflow preventer should be isolated so compressed air is not forced through it. Work through zones slowly, stopping when the sprinkler heads emit mostly air and a fine mist; the report advises two passes and turning off the compressor before changing zones.
Pressure and equipment matter. The report says airflow, measured in CFM, is as important as pressure because it affects how much water the compressor can move. It cites about 5 CFM for many residential systems when working one zone at a time, not as a universal specification. It also warns against excessive pressure or continuing to blow air after a zone is clear: either can damage heads, fittings or seals. Wear safety glasses, keep people clear of pressurized equipment, and consider professional help if the system is unfamiliar or the procedure cannot be done safely.
Freeze Damage Can Hide in Lines
Winterizing matters because damage may not be visible until the system is turned on again. A cracked valve or split fitting can mean spring repairs, water loss and disruption to lawn or garden watering. Simply shutting off the supply can give a false sense that the system is protected if trapped water remains.
At the same time, a blowout is not risk-free. Compressed air can send water or debris flying, while excessive pressure can damage irrigation parts. The practical choice is not to use air at any cost, but to follow the system’s instructions, use suitable equipment and seek a qualified irrigation professional when needed.
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Timing Depends on Local Freezes
The report advises completing winterization before the first hard freeze. In colder regions, that may mean early or mid-fall. It says an established lawn can generally tolerate irrigation being shut off somewhat early and will green up again when watering resumes in spring.
Exposure varies across a system. Above-ground backflow preventers and exposed pipes face freezing air first; buried lines become vulnerable as prolonged cold drives frost deeper into the ground. Some mild-winter areas have systems without a blowout port, where shutting off the supply and draining exposed components may be sufficient. The report’s instructions are general guidance, not a substitute for a system’s manufacturer directions or local advice.
““That valve keeps new water out, but the water in the pipes, valves, and heads stays put.””
— Gardening Know How report
System Needs Vary by Site
The report does not establish a single winterizing method or compressor setting for every property. The right approach depends on system design, pipe layout and local freeze conditions, and the source does not provide a pressure limit that can safely be applied to all systems. It also cannot confirm whether an individual system’s low points have drained fully. Homeowners should check their irrigation documentation or consult a qualified professional if the setup, blowout connection or safe operating limits are unclear.
Prepare Before Temperatures Drop
Homeowners should check the local forecast and arrange winterization before a hard freeze is expected, allowing time to identify the water shutoff, drain points and any blowout connection. If using compressed air, follow the system maker’s instructions, use eye protection, open only one zone at a time, and stop once it is cleared rather than running air through dry lines.
After the procedure, the report says to leave the backflow preventer’s ball valves and test cocks half-open to reduce the chance that trapped water will freeze there. In spring, inspect the system for leaks or cracked parts before returning it to normal watering. The report does not give a date for any follow-up guidance; the immediate deadline is local weather, not a single calendar date.
Key Questions
Is turning off the sprinkler water enough for winter?
Not always. The report says water may remain in pipes, valves and sprinkler heads after the supply is shut off. Whether further draining is needed depends on the system and local freeze risk.
When should I winterize my sprinklers?
Complete the work before your area’s first hard freeze. In colder regions, the report says that often means early to mid-fall; local weather and system guidance should shape the timing.
Can I blow out sprinkler lines with any air compressor?
No single compressor setting fits every system. The report cites about 5 CFM for many residential systems when clearing one zone at a time, but says airflow and pressure both matter. Check the system’s instructions or ask a professional before connecting a compressor.
What safety precautions should I take?
Wear safety glasses, keep people and pets away from pressurized heads and fittings, and never force air through a closed valve or through the backflow preventer. Turn off the compressor before switching zones, and stop blowing once a zone is clear.
Source: rss
