How To Winterize Your Lawn Sprinkler System

By London Fog

March 11, 2021


Do sprinklers really need to be winterized? 

If you live in a region where the temperatures regularly drop to or below freezing, you really do need to winterize your sprinkler system.

This is not a long or arduous process, but if it is not done then you could potentially be looking at some very costly repair jobs come springtime.   

winterize your lawn sprinkler system

This is not true of much of the world where the temperatures do drop to this level.

If you do not winterize your system you are likely to need to dig up your entire lawn come spring to repair irrigation lines.  

Can I just drain my sprinkler system for winter? 

Yes, you can. This is effectively what winterizing a sprinkler system is. That being said, simply draining does not completely guarantee that all pipes and sections of the sprinkler system are completely devoid of moisture.

Any residual water left in the system has the potential to freeze and cause damage.  

For this reason, it is advised to perform a blowout of the system before completely shutting it down. This ensures that as much water as possible is removed from the system. This can be difficult to do without the correct knowledge, and many people opt to hire a professional to complete this.   

How do I drain my sprinkler system for winter? 

You will first need to turn off the power source for your sprinkler system and switch off the water supply too. If you have any devices connected to the sprinklers for monitoring, you should disconnect these now too.   

If you have drain valves installed on your pipes, open these and allow any residual water in the system to flow out. If you do not, we suggest using the blowout method. This uses an air compressor to send pressurized air through the pipes, forcing out any remaining water.

The air compressor needs to have enough horsepower to be effective. That being said, you do not want the air pressure to reach above 80 PSI as this can damage your sprinkler system.  

What happens if you don’t winterize your sprinkler system? 

If you do not winterize your sprinkler system this can cause a lot of problems, such as cracks in your pipes and fittings.

This is caused by the water expanding as it freezes, increasing the pressure on the pipes. In a similar manner, sprinkler heads, backflows, valves, and anti-siphon devices can become damaged or irreparably broken.   

Even if no damage is immediately apparent, there could be small cracks and fissures along the water pipes. This can then cause leakages and severe water damage if not dealt with swiftly.

By not winterizing your pipes you are leaving your system open to sustaining potentially thousands of pounds worth of damage.   

When should I turn off my sprinkler system for winter? 

There is no specific time at which you should switch off your sprinkler system for winter each year. You should take hints from the ambient temperatures in your region and use this to guide your decision.  

Water freezes at 32 degrees Fahrenheit. You should switch off your system before the temperatures in your area are consistently reaching this figure, or dropping below.

This is the best way possible to protect your pipes and the rest of your system. It means that there is very little chance of the water in your pipes freezing and causing knock-on damages.   

How much does it cost to winterize a sprinkler system? 

The cost of winterization varies according to a number of factors. These include the number of zones you have in your yard and the type of sprinkler system that you have. There are many reputable companies online that you can contact to get a personalized quote.  

Hiring a professional will likely set you back between $50 and $250. Many companies will offer winterization packages that include the setting up of the system in the spring, which often falls towards the higher end of the price bracket.   

If you choose to DIY the winterization, you can rent air compressors from hardware stores for as little as $20 per hour.   

Will underground sprinkler pipes freeze? 

The underground sprinkler pipes are insulated by a layer of soil, so you would be forgiven for thinking that they won’t freeze.

This is actually not true and underground pipes are still highly susceptible to freezing at low temperatures.   

Do you need to blowout your sprinkler system? 

Yes, it is always a good idea to blowout your sprinkler system as part of the winterization process. You should not blow through any circuit for longer than a minute at a time, to avoid damaging the pipes and fittings.  

The pressurized air is designed to force water out of the internal pipes. When you are performing the blowout, do not stand over any parts of the sprinkler system as if the pressure is too high, parts can begin to fly off.   

What PSI blows sprinklers? 

As mentioned above, 80 PSI is the absolute, hard limit for the pressure that top of the range sprinkler systems can withstand. It is a good idea to not exceed 50 PSI when dealing with irrigation systems as this can cause damage to the inner mechanisms.  

Your compressor will need to be capable of producing an air volume of 20 – 25 cubic feet per minute.

This combination of high volumes and low pressure means that the blowout process will be most effective and cause the least damage to the sprinkler system.   

Even if your sprinkler system can withstand 120 PSI of stated water pressure, do not be fooled into thinking that this translates to air pressure. Air has a lower viscosity than water which means that air at the same pressure will damage the system.   

How do I manually turn off my sprinkler system? 

The first thing to do is to go to your controller panel. There should be a switch labeled ‘Off’ or ‘Rain’.

Press this to stop the flow of water. Do not attempt to unplug the controller as this can cause real issues with your sprinkler schedule. If it is still on after this, check the valves.   

There is a shut-off valve in all sprinkler systems, found near the water source. This can be turned to the off position to ensure water is no longer being sent to the sprinklers.   

Your system may also have a backflow prevention device – a green rectangle or oval. This is commonly found near to the road and your water meter. If it has a ball or gate valve, turn the handle clockwise.  

How do I know if my sprinkler system is self-draining? 

These systems are also referred to as automatic sprinkler systems. When purchasing a system you should be able to ask the seller or manufacturer if the system is self-draining.   

If it is, then winterizing will be a breeze. Simply turn off the water supply and timer. Open each valve on the system with one full turn. This will activate the self-draining function which takes less than 5 minutes to complete. There is no need for blowouts on self-draining systems.   

Can a dry sprinkler system freeze? 

Yes, they can.

But a dry sprinkler system is actually a fire suppression system and not a lawn care system.

But to answer the question, they are commonly found in warehouses and parking lots where a wet fire sprinkler system would freeze.   

Dry sprinkler systems operate through the use of  air in the pipes. This air prevents valve actuation.  The valve, located in a heated room has air on one side and water on the other.  When a fire event happens, the air evacuates, the valve opens, and water flows to suppress the fire.

Dry sprinkler systems can freeze as the air contained within the pipes has moisture in it. This can then condense in the lower points of the sprinkler system pipes, and then freeze.   This is one reason dry systems have such rigid inspection and maintenance requirements.

How do I turn my sprinkler system back on after winter? 

This is a relatively easy procedure and only requires a few tools. These are a flat-head screwdriver, a sprinkler valve key, pliers, a pen, and some paper.   

Your first step is to find the main shut-off valve for the system, often located near the control box. You should then look for the vacuum breaker. This is often found above ground near your home. It is commonly made from copper or plastic and will connect 2 pipes.   

Close the test valves on the vacuum breaker using the flat-head screwdriver. When they are shut off the slot will be perpendicular to the stem. You will then need to open the shut-off valves by turning the handles. These should be parallel to the respective pipes.   

If you need to, reinstall the main valve bleeder cap. Slowly open the main valve, allowing the water to turn on gradually. It is vital to do this slowly. If the water is turned on too fast it creates a water hammer which can cause severe damage to your pipework.   

Run a manual test of each zone for a few minutes at a time. Initially, this will cause air to blow out, but soon water should begin to appear. Check the system for any leaks or damages and then you’re good to go!