DIY: Winterize your Sprinkler System

Since becoming a homeowner a year and a half ago, I have had to learn a few things, one of them being how to winterize a sprinkler system.  Yes, I could hire someone to winterize my sprinkler system but that would cost me a fair amount of money (I think it’s around $100) so, within a few years I would have all of my equipment paid off (not to mention, an air compressor is nice to have for other DIY projects such as changing a timing belt (an impact gun is nice for motor mounts…)).

Disclaimer:  You can ruin your sprinkler system if this is done wrong!  I am only telling you what has worked for me, if your system is different, consult the manufacturer or installer.  For the record, if you screw up your sprinkler system, (I feel bad for you but it isn’t my fault!!  Another good way to figure it out would be to hire someone then follow them around…  That way you only have to pay one year!

To start out with you will need a few tools:

1. Air Compressor:  I bought a Craftsman air compressor (1.6 HP 26 gal tank), I can tell you right now, that isn’t the best option for this…  You really need a larger pump/motor, probably ~2.5+ HP.  The problem is flow rates, The 1.6 HP air compressor I have has a flow rate of about 4.8 scfm (standard cubic feet per minute) @ 90 psi.  To really do this right, you probably need more like 10+ scfm @ 90 psi.  It is doable with a lower flow rate but it takes a lot more time, it’s not the ideal solution.  The most important part of the air compressor is that you do not let more that 100 psi go into the sprinkler system.  Use a regulator to keep the pressure down! I use around 90 psi to be safe.
2. Flat head screw driver:  really, it’s probably best to have 2 of these, I use a large flat head to open my valve box and a small one is needed for the valves on the back-flow preventer.
3. water shutoff tool:  Some people might be fortunate enough to have the valve inside or possibly just a shutoff somewhere that has easy access, for the rest of us, our valves are 3+ feet below the ground…  there is a small tube that we have to stick our tool into to turn off the water.  Some people have a “T” tool to do this, I use a piece of plastic electrical conduit with the end cut so there are two fingers to grip the valve handle as shown below (make sure to label the directions to make your life easier in the future):

That is really about it for tools needed.  You will have to buy one more valve setup that I will discuss later but you can leave that on your sprinkler system after you buy it.

Next you will need to locate the components that are part of your sprinkler system.

1. The Control box:  Mine is in my Garage, it is a hunter brand sprinkler system.  You will want to understand how this works so you can run the system in manual mode to clean the water out of the lines.
2. The Water valve box:  The installers/previous home owners were nice enough to put this right in the middle of my front yard…  Because I needed one more odd thing in my small front yard.  As far as I know, the green covers are fairly standard for sprinkler systems.  You will notice the second picture has a valve with a duct taped end, that was something I added, it originally had a PVC threaded cap on the end, we will get to this part later
3. The Back-flow preventer: This is along the side of my house next to the control valve box (#4).  It’s a goofy looking part that is apparently fairly expensive (so don’t let it freeze with water in it).  There are normally 2 valves in line with the back-flow preventer.  If you didn’t already know, the back-flow preventer (most often required for irrigation systems that connect to the public water lines) prevents water from flowing back into the public water lines, this is done to prevent contamination of drinking water.  Here is a picture of my back-flow preventer, I think most residential back-flow preventers look similar to this:
4. Control Valve box:  This is a fairly large rectangular box not far from the back-flow preventer.  It houses all of the control valves which contol flow to the different zones.  My system has 6 zones, I think the control box could theoretically control either 8 or 9 different zones depending on how large your yard is.

Ok now that you have gotten all of that together and figured out where everything is, it’s really a fairly simple process.  First thing that you need to do is buy, assemble and install the valve for the airline (the pipe with the valve on in in the water valve box).  I bought a kit from the airline fitting section at Home Depot, it included a valve, the male air hose fitting and the correct size fitting to convert from the pipe to the valve (seems like it was 1 1/8th in)  assemble these parts and install as shown in the below picture:Once that is set up, you can start the winterization process.

I normally run my sprinklers for a few minutes before hand, this is done for a few reasons; so I can make sure they are working correctly (they run around 5AM so I never see them running), I get a visual picture of where all of the sprinkler heads are at and I normally spread Scotts winterizer fertilizer afterwords, the grass needs to be wet when you spread the fertilizer.

Step One:  Turn the water off.

Take your water shutoff tool and slide it down the pipe that contains the valve (in the water valve box)  as pictured below:

Make sure to turn it the correct direction (if the water is on, it will probably only turn one direction)  To check if the water is off, turn one of the zones on, if water is still coming out continually,you probably didn’t get it turned off.

Step Two:  Attach the air compressor.

Connect an airline to the air compressor and to our nice little valve assembly we just installed (or previously installed).  Apparently I didn’t take a picture of this but it really shouldn’t be to hard to figure out.  Make sure to have the valve in the off position, you could rupture the line if you apply to much pressure with no way for it to escape.

Step Three: Spray the zones out.

I like to go in order so, go to your control box and turn on the manual mode for zone 1.  Make sure you have plenty of time so add 15 minutes  to the time the zone will be one for.  Once you have a zone turned on and your air compressor is ready (**Don’t run more than 100 psi through the lines, they could burst or the sprinkler heads could break even with the zone on!!!!**) open the  air valve in the water valve box.  If you have a relatively low flow air compressor (which I do), you will have to watch the pressure and turn the valve off and let the pressure build back up before you continue on.  Below there are pictures of what the sprinkler heads should look like when you first start flushing them (the first picture below) and then when you can stop (the last picture).

This picture shows what a zone looks like as the sprinkler heads start to clear but some heads still have plenty of water in them that still needs to be cleared.

When the all of the sprinkler heads in this zone have either just air or just a fine mist coming out (below), you can change to the next zone and repeat this step until you clear all of your zones.Finally, once I have all of the zones clear, I like to cycle though them all one last time just to make sure they are clear.

Step Four (the final step):  Ready the back-flow preventer for winter.

This is a simple task but it is very important because as I said, the back-flow preventer is fairly expensive and depending on where you live, you would have to get it inspected when you install a new one.  There are really only two tasks involved in readying the back-flow preventer for winter: 1. Turn the vavles on either side of the back-flow preventer so they are half open, 2. Open the valves on the back flow preventer half way.  This will make sure that if there is any water in the back-flow preventer, when it freezes, it will have a place to expand and escape.  Below are a few pictures, first shows the valves on either side of the back-flow preventer at a 45 deg angle to let water escape.

This picture shows the two drain valves on the back-flow preventer.  These both need to be turned so they are partially open (turn 45 degreed from horizontal/vertical) to let water escape.

A few extra tips that might be helpful:

When half of a zone is spraying out air and the other half is still spraying out water, I push one of the heads, that have just air coming out of them, down so the air will push more water out of the heads that still have water in them.

Depending on the air compressor you have it could take anywhere from 30 minutes to a few hours to complete this task but it is worth the time it takes you because you wont have to spend around $100 to have someone winterize it and an additional $60 for someone to come turn your sprinkler system on in the spring.

That brings up another point:  Turning your sprinkler system on in the spring:  All I really do is:

1. open the valves on either side of the back-flow preventer
2. close up the two valves on the back flow preventer
3. turn the water on
4. turn the Control box on
5. run the sprinkler zones in manual to make sure all of the heads are spraying in the proper directions
6. turn the Control box to Auto and let her buck!

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