Sprinkler System Winterization Checklist
Sprinkler pipe is buried shallow, and water left in a lateral line, a zone valve or the backflow preventer expands as it freezes. The crack stays hidden all winter. You find it in April as a soggy strip of lawn or a zone that will not hold pressure.
Systems drain in one of three ways. Some have manual drain valves at the low points, some have automatic drains that open when the pressure drops, and many cold-climate systems have neither, so the lines have to be blown out with compressed air. Find out which one you have before you start. The steps below are grouped that way, so skip the groups that do not apply.
The backflow preventer is the most exposed part. It usually sits above ground by the house with nothing around it but air, so drain it and wrap it even if a contractor blows out the rest of the system.
- Find the irrigation shutoff valve, the backflow preventer and the controller — The shutoff is usually in the basement or a valve box near the water meter.
- Work out whether your system has manual drains, automatic drains or neither — The installer's paperwork or a look inside the valve boxes usually tells you. Neither means a blowout.
- Book an irrigation company now if you will not do the blowout yourself — Fall blowout slots fill up in the weeks before the first freeze.
- Turn off the water supply to the system
- Set the controller to off or rain mode — That stops it opening valves all winter, and keeps your zone schedule for spring.
- Manual drains: open every drain valve at the low points and let the lines empty — Close them again once the water stops running.
- Automatic drains: run each zone for a minute or two after the supply is off — This drops the pressure so the drain valves open. Water can still sit in the valves and the backflow preventer, so drain those by hand.
- Blowout: put on safety glasses and keep everyone clear of the heads — Air and grit leave the heads hard enough to hurt.
- Connect the compressor at the blowout port downstream of the backflow preventer — Never push air through the backflow preventer itself. It can damage the device.
- Open one zone at the controller before any air goes in — With every zone closed, the air builds pressure in the main line with nowhere to go.
- Use the pressure your installer or system maker gives, and no more — Too much pressure cracks fittings and blows heads apart.
- Blow out each zone until only mist comes from the heads, then move to the next — Do not keep air running through a line that is already dry. Friction heats the pipe and can damage fittings and seals.
- Go round every zone a second time, briefly — After the first pass, water still in the pipe runs down into the low spots.
- Use the drip maker's lower pressure limit on drip zones — Drip tubing and emitters are built for far less pressure than spray heads.
- Disconnect the compressor and release the air left in the system
- Drain the backflow preventer by opening its test cocks
- Wrap the backflow preventer and any pipe above ground in insulation — Use a cover made for backflow devices, or foam pipe wrap and a bag, and keep the test cocks reachable.
- Drain the irrigation pump, if your system has one
- Bring the drip zone filter screen inside, or clean and dry it
- Check the shutoff valve a day later for drips — A valve that lets water past slowly refills the lines you just emptied.
- Flag the heads along the driveway and sidewalk — A shovel or a plow blade snaps a head it cannot see under snow.
- Write down every broken head or weak zone you noticed this year — Spring repairs go faster when the list already exists.
- Note when your backflow test is due, if your water utility requires one