When you fail to winterize an irrigation system, chances are your pipes will freeze from the extreme cold, which can eventually lead to them breaking.
Once that happens, it's possible for your pipes to leak once the cold weather ends and everything thaws out.
Any water left in the pipes of an irrigation system can freeze solid if you live in an area with freezing temperatures and snow, and depending on your climate, that risk can start well before the first real snowfall of the season.
In this guide
Pipes Freeze and Burst
When the ground freezes, it leaves exposed and underground pipes vulnerable.
Water expands as it freezes, and that expansion inside a rigid pipe is what causes the pipe itself to crack or burst, since PVC and similar materials simply aren't flexible enough to absorb that added volume.
The frustrating part is that you often won't notice a cracked pipe right away. The break may not actually leak until the ice inside it thaws again, which usually doesn't happen until you turn your system back on in spring.
How to Drain Your Sprinkler System
Manual Valves
If your sprinklers have a manual drain valve, you'll have to manually open all of the air vents to drain the system. Turning off the water supply is the first step.
A backflow preventer should already be installed to keep water from flowing back into the house. Make sure this valve is closed so that all of the water from the sprinklers flows out and away from the house instead.
From there, you let gravity do the work, draining water out of the pipes at the system's lowest points.
Check for any check valves or backflow preventers that could be stopping water from flowing freely out of the system, and open them.
Close all of the valves fully once the water has been drained.
Manual drain outlets aren't always enough on their own. Some water can still get trapped in the low spots of the pipes and fail to drain out through the sprinkler heads.
You can guard against this by adding a bit of antifreeze to the pipes, or by using a compressed-air blowout, which we'll cover below.
Automatic Valves
Some sprinkler systems have automatic valves that drain water out of the pipes once the air pressure inside drops below a certain number of pounds per square inch.
Typically, the operation manual for these systems will include instructions on how to do this correctly for your specific setup.
To activate the automatic drainage, turn off the water supply and run just one sprinkler head until the water has drained out.
Your system might have a switch on the control panel that starts the drainage process, or it may kick in automatically (an auto-drain valve).
To make sure all of the water is removed, you'll still need to manually open any check valves and backflow devices in the system.
Water Damage
If you leave water in the pipes while the ground around them is freezing, you're likely looking at problems once the soil thaws.
You might get lucky: if your sprinkler system isn't winterized but the freeze is mild and the lines sit deep enough below the frost line, you may escape without any major damage.
Unfortunately, if your sprinkler system isn't winterized and a hard freeze does occur, there's a real risk the sprinkler lines will crack, leading to leaking sprinklers the following spring and summer, or, in the worst case, water freezing and expanding inside the pipes badly enough to cause major, costly flood damage to both your house and your sprinkler components.
Note that "winterizing" your sprinkler system (removing water in the fall so it doesn't freeze) and "spring start-up" (getting the system running again once the weather warms) are two separate seasonal services, not the same thing.
When your sprinkler system is winterized, all the water is forced out of the system, typically using an air compressor, to keep any trapped water from freezing inside the pipes during cold weather.
You'll Be Paying a Lot of Money To Repair Your System
The blowout method removes all remaining water from the pipes and protects the sprinkler system for winter.
Done correctly, this technique forces all of the water out of the sprinkler system, eliminating any real possibility of freeze damage during the winter months.
As mentioned above, you could also add a little antifreeze to the pipes to help prevent freezing, as an extra layer of protection alongside draining or blowing out the lines.
If the water is simply shut off, but never actually flushed or blown out of the lines, you won't find out about any resulting damage until spring rolls around.
Winterizing a system means draining the lines or blowing them out with compressed air, so it's essential to do this before the ground starts to freeze.
For anyone unfamiliar with the process, winterization means clearing all of the water out of your entire sprinkler system, including the heads, pipes, valves, and pump, before it has a chance to freeze and cause damage and costly repairs down the line.
Unlike the water pipes running through your house, sprinkler systems need this annual blowout, since without it, freeze damage often goes unnoticed until spring.
Failing to properly prepare your irrigation system and sprinklers for the colder months will lead to damage and leaks that typically aren't noticed until spring, when you turn the irrigation system back on.
Conclusion
Your best bet is to get your winterization service done before temperatures begin to drop significantly. If a cold front moves in early and you haven't taken care of your system yet, you'll likely regret it come spring, facing expensive repairs.
Save yourself money and headaches with a little maintenance in the fall to make sure your system is ready for a harsh winter.
As eager as you might be to get your lawn back to its lush green state each spring, keep in mind that temperatures of 32°F or lower put your lawn sprinklers at risk of freeze damage, so don't rush to turn the system back on until you're confident hard freezes are behind you for the season.
To activate an auto-drain valve, shut off your water supply and run just one sprinkler head until the excess water has been removed.
