Winterizing Your Irrigation System

If you have a sprinkler system, shutting it down in the winter is one of your tasks as a homeowner. Without winterizing your irrigation system, you risk water freezing in your pipes, causing major headaches. We share how to winterize your irrigation system in six key steps.

Ways to Drain Your System

There are three ways to drain and prepare your residential irrigation system for winter:

Manual
Automatic
Blow-out (air compressor)

Manual and automatic draining allows all the water to leave the system through gravity and an open valve. These methods of draining are the least efficient, according to Colorado State University Extension. Water is not thoroughly removed from the pipes and could freeze.

Blow-Out Method

The blow-out method of draining your system is the most efficient way to remove water from your pipes. If you have a small system (lot size 1/4 to 1/2 acre), blowing out your system yourself is a simple DIY project.

This article takes you step-by-step through winterizing your sprinkler system with an air compressor. However, consulting a professional is highly recommended if your lot is over 1/2 acre.

Parts of Your Sprinkler System

The main parts of your irrigation system involved in winterizing are:

Valve box
Shut-off valve
Test cocks
Backflow
Irrigation controller

Steps to Winterizing your Irrigation System

There are six key steps to getting your sprinkler system ready for winter.

Step 1: Turn off the water to your system

The shut-off valve will usually be in one or two places. The first is outside, in your lawn, in a valve box.

The second is inside your home. The shut-off valve in your home is typically somewhere in the basement or crawlspace.

Step 2: Drain the backflow.

With the water supply shut off, you can now open the test cocks on the side of the backflow. Open them slowly.

illustration of test cock location — Test Cock Illustration

At this point, there is still pressure on the irrigation system. As you open the test cock, water will come out.

Don’t stand directly in front of it, or you will get wet. It only takes a few seconds for the backflow to drain.

Step 3: Relieve water pressure from the rest of the system.

Relieve water pressure from the rest of the system by going to your irrigation system controller, selecting a zone to come on, and pushing the “manual start” button.

Choose the zone that is farthest from the backflow and work your way back towards the backflow. Opening zone valves relieves the water pressure from the pipes that are underground.

Don’t expect to see a lot of water shooting through the air. This step is all about relieving pressure. At most, a quick spurt of water will shoot out of a sprinkler head or two.

Step 4: Pressurize your irrigation system with air.

Pressurizing your system with air is a fun step, but you need to take a few precautions. You are adding air pressure to your irrigation system. Glued PVC pipes and PVC fittings make up most irrigation systems. These pipes and fitting are only so strong. Adding too much pressure can damage them.

General recommendations are to never go above 80psi (Pounds per Square Inch) on the air compressor.

Another safety recommendation is always to wear safety glasses while blowing out your irrigation system.

You are working around compressed air, water, and soil. You don’t want to have something fly through the air and hit you in the eye.

Next is the compressor; you will want to use a compressor that produces sufficient psi and air volume. A small compressor you use to inflate tires or use in a shop can probably produce 80psi, but it won’t be able to deliver the air volume needed to push all the water out of your irrigation system.

If you do have a larger compressor, great, you are ready to get started. If you don’t, you can rent one from your local equipment rental business.

Connecting the air compressor to your irrigation system is where it can get a little tricky. Through my experience, often, there isn’t a connection fitting ready to receive the compressor fitting.

**WARNING** Don’t take the easy route of connecting the air compressor fitting directly to the backflow. Blowing compressed air through the backflow can damage it.

The backflow is one of, if not the most expensive, pieces of your entire irrigation system.

Don’t make that costly mistake.

This step is where you can use some of your ingenuity to solve the problem. You can get the proper air compressor fitting to connect to your irrigation system for a few dollars in supplies.

How your backflow connects into the rest of the irrigation system determines what supplies you will need. The two most common materials used on irrigation systems are PVC and copper.

Once you have the correct fitting, you will have it forever. Having this fitting makes the following year’s irrigation system shut down even more straightforward.

Step 5: Turn on the compressor and open the irrigation valves.

Connect the compressor to the irrigation system. Now turn on the compressor. At this point, keep the compressor valve closed, and remember, don’t go above 80psi.

Next, go to the irrigation controller, and open your first valve. This process is a repeat of Step 3. Then slowly open the compressor valve.

Doing this allows air to flow from the compressor into your irrigation system. You will hear your irrigation heads popping up, and water will begin shooting out of them.

blowing out irrigation — Blowing Out Irrigation

After a few minutes, you will start hearing a different sound. This sound is the air starting to mix with the water.

You now turn off that zone and go to the next zone. You repeat this process through all of the zones on your irrigation system.

I suggest going through all of your zones twice. This routine removes the water and is better for the other irrigation components that make up your system, particularly the rotors.

Rotors are the irrigation heads with a continuous stream of water coming out of them, and they rotate back and forth. Inside these rotors are plastic gears.

Suppose you were to push air through the rotors for an extended amount of time; the heat generated as the air passes through them could damage them.

It is better to go through your system twice for short periods than to get all the water out at once.

Step 6: Protect the Backflow.

If your backflow connects to the irrigation system with unions. I recommend removing the backflow and taking it inside for the winter.

Once it is drained and protected from freezing temperatures, it will not freeze and be ready to go the following spring.

I also recommend covering or closing any openings in the backflow or piping to keep out any mice or insects looking for a winter vacation home.

You will want to do the same thing for the pipes that are still outside. I have found that vinyl gloves or sandwich bags wrapped with duct tape do an excellent job at keeping out little critters and other small debris.

protected backflow pipe — Protected Backflow Pipe

If you can’t or don’t want to remove the backflow, leave all valves and test cocks half-open. This precaution gives any water that might get into the backflow a chance to escape.

Sometimes main shut-off valves are not closed completely. Water, then, slowly trickles through the pipes and back into the backflow.

If the backflow valves and test cocks are not open, the backflow fills with water and bursts the next time temperature reaches 32ºF (0ºC).

Wrapping the backflow with an electric pipe heating cable and insulation creates an extra layer of protection but only works as long as power is available.

Helpful Tip to Save Money

Because blowing out a small irrigation system only takes 30-45 minutes per house, neighbors pooling their money to rent an air compressor can save money. Each neighbor that contributes gets their system blown out within that rental period.

Irrigation systems help us keep our gardens and landscapes thriving, beautiful, and healthy. Just like everything else, an irrigation system needs maintenance and attention to keep it working correctly. Winterizing your irrigation system is a critical piece of that process.

We walk you through the steps in our video.

As always, if you are unsure about this process, consult a professional.