Jess Stryker's Landscape Tutorial Series, Winterizing your Irrigation System.

Jess Stryker's Landscape Irrigation Tutorials
Winterizing Your Irrigation System

Don't forget about spring "start up" procedures!

The Basics

Winterizing your irrigation system is really pretty simple:

    1. Turn off the water to the irrigation system at main valve.
    2. Set the automatic irrigation controller to the "rain" setting.
    3. Turn on each of the valves to release pressure in the pipes.
    4. Drain all of the water out of any irrigation components that might freeze.

Be sure to check out the glossary if you find a term you don't understand!

Well, you could probably figure out those basic steps without my help! What you want is details, so let's get to it. Depending on where your irrigation system is located you need to take different approaches to winterization.

Select your location:
Temperate Climates
Cold Climates

Temperate Climates

These are areas where it doesn't freeze or a typical freeze lasts for only a few hours. If it snows the snow melts in an hour or so. Ice may form at night but quickly melts in the morning. If you have hose bibs or water pipes on the outside of your house chances are they are not wrapped in insulation to keep them from freezing (because they don't need to be!).

Ahh, the joys of Southern California living! Here we consider anything below 60 degrees (F) much too cold and we pull out the parkas and throw a log on the fire! Well, OK, I live in the southern fringe of Central California, but I'm only about 2 blocks from the ocean so it almost never freezes here. However, throughout most of Southern California, like other temperate regions, we can get hard freezes during the early morning hours. Any freeze can cause damage to an irrigation system, so precautions need to be taken.

Here's the procedure for all temperate climate areas:

    1. Shut off the water supply to the irrigation system. The main shut off valve for your irrigation system needs to be "freeze proof". That means it should be below the frost line, inside a heated room, wrapped with insulation, or somehow protected from freezing. It doesn't do much good if the shut-off valve freezes and breaks! So what happens if you don't have a main shut-off valve for your irrigation system? Then you'll need to install one! (duh!)

    2. If you have an automatic system then you will need to "shut down" the controller (timer) also. Most controllers have a "rain mode" which simply shuts off the signals to the valves. The controller continues to keep time, the programming information (start times, valve run times, etc,) isn't lost, and the clock continues to run, all that changes is that the valves don't come on. An alternative to using the rain mode is simply to shut off the power to the controller. If you do, you'll need to reprogram the time, and maybe all your other settings too, in the spring! How much electricity is saved by turning it off? That depends. Solid state controllers use very little energy-about the same as a night light. Mechanical controllers use more- as much or more than a 100 watt bulb in many cases. My rule of thumb is that if the controller has a digital time display you should use the rain setting on the controller. If the controller uses a dial, like a analog clock face, turn off the power to the controller to save electricity. If a pump is wired to your controller you should disconnect the power to the controller rather than using the rain shut down feature. There is a remote possibility that the controller could damage the pump by accidentally starting it while the system is shut down.

    3. In temperate areas it is not necessary to remove the water from the underground pipes since it doesn't freeze that deep. Hooray!

    4. If you have gear-drive rotor sprinklers installed above ground the water needs to be drained out of them or they may freeze and rupture. Often the water will drain out on its own. If the water doesn't drain out you will need to install a drain valve somewhere on the sprinkler supply pipe so you can drain the water out. A 1/2" valve will work fine. Another option is to remove the rotors and shake the water out of them, then replace them (or store them inside for the winter). Many rotors have a built in check valve that prevents the water from draining out, so you have to remove them and shake the water out. So if you have any gear-drive rotors mounted above ground be sure to check to make sure the water has drained out of them.

    5. Any above ground piping needs to be insulated. You can buy self sticking foam insulating tape to wrap around the pipe which works fine. You can also install the foam insulating tubes commonly sold at home supply stores on them. (Buy a couple of extra lengths of foam for the kids, they love to use them for "sword" fights. Also, if you have a low doorway the foam tubes make great bumpers to keep you from getting your brains knocked out when you forget to duck on your way out the door!)

    6. Insulate backflow preventers and valves (or remove and store them) if they are above ground. You can also use insulation tape for this. Do not block the air vents and drain outlets on backflow preventers! A cheap trick is to get some R-11 fiberglass insulation and wrap it around the valve or backflow preventer. (Crumpled up newspaper will also work for emergency insulation!) Then place a heavy duty plastic trash bag over the whole thing to keep it dry and use duct tape to hold it all in place. (For a more permanent installation you may want to use heavier plastic than a trash bag!) Don't seal the bag tightly, allow for an air passage at the bottom so water can run out and air can flow in! Just wrap it tight enough to keep the bag and insulation from blowing off. Insulation will not work if it gets wet! You can also buy ready-made insulation blankets for your valves and backflow preventers at most sprinkler supply stores. (You may need to special order them.) These consist of a large bag made from fiberglass filler sandwiched between soft vinyl cloth, much like a sleeping bag. This insulated bag goes over the backflow preventer and ties or padlocks in place. One brand that I have used is "Polar Parka". They get a free plug because they sent me a small sample insulation bag, about the size of a bed pillow! I carry it in my truck where I use it as an emergency pillow, a hand warmer, or a great place to put six-packs of soda to keep them cold during the summer!

The nice thing about all the above items is that you can do them once, then you never have to worry about it again. The insulation can stay in place all year long and you don't ever need to worry about winterizing again. (Which isn't to say that you should neglect your irrigation system. You should still do pre-season maintenance each year in early spring! See the section on Spring start-up procedures.) After all, isn't that why you choose to live in a nice, temperate climate location?

Cold Climates

Chances are if you live in one of these climates I don't need to provide a definition of "how cold is cold" for you! If you ever need to shovel snow, or if ice forms and doesn't melt for days on end, then you are in an area where you need to take some major measures to protect your irrigation system from freezing.

Here's what you need to do if you live in a cold climate area.

    1. Shut off the water supply to the irrigation system. The main shut off valve for your irrigation system needs to be "freeze proof". That means it should be below the frost line, inside a heated room, wrapped with insulation, or somehow protected from freezing. It doesn't do much good if the shut-off valve freezes and breaks! What if you don't have a main shut-off valve for your irrigation system? Then you'll need to install one! (duh!)

    2. If you have an automatic system then you will need to "shut down" the controller (timer) also. Most controllers have a "rain mode" which simply shuts off the signals to the valves. The controller continues to keep time, the programming information (start times, valve run times, etc,) isn't lost, and the clock continues to run, all that changes is that the valves don't come on. An alternative to using the rain mode is simply to shut off the power to the controller. If you do, you'll need to reprogram the time, and maybe all your other settings too, in the spring! How much electricity is saved by turning it off? That depends. Solid state controllers use very little energy-about the same as a night light. Mechanical controllers use more- as much or more than a 100 watt bulb in many cases. My rule of thumb is that if the controller has a digital time display you should use the rain setting on the controller. If the controller uses a dial, like a analog clock face, turn off the power to the controller to save electricity. If a pump is wired to your controller you should disconnect the power to the controller rather than using the rain shut down feature. There is a remote possibility that the controller could damage the pump by accidentally starting it while the system is shut down.

    3. Remove the backflow preventer, remove water from the risers, and cap the risers. (If you are lucky you can siphon the water out of the risers. More likely you will need to pump it out. I've found a wet/dry shop vacuum works fine with a few modifications. The hose on the vacuum is usually to large to work, you will probably need to rig a smaller hose onto it using duct tape.) Drain the water out of the backflow preventer and put it in storage for the winter. (You can reinstall it after the water's drained out if you want to, but I prefer to store it out of harm's way.) If you have valves installed above ground you need to drain the water out of them, it's a good idea to remove and store them also. An alternate method is to install pipe heating cables on the above ground valves and backflow preventer then install insulation over the heater cables. Of course you'll have to pay for electricity to run the heaters all winter, and if the electrical power goes off for an extended period... crack!

    4. While we're on the subject of backflow preventers, your backflow preventer, along with any above ground pipe, should have permanent insulation installed on it. This is to protect it from those unexpected early and late season freezes! Those freezes are generally light, so insulation will give you the protection you need. Backflow preventers are very expensive to replace. A few years back an unexpected freeze resulted in so many broken backflow preventers that for a short period it was impossible to buy one due to lack of availability! One way to insulate the pipes and backflow preventer is to use the self-stick foam insulation tape which is available at most hardware and home supply stores. Do not block the air vents and drain outlets on backflow preventers! A cheap trick is to get some R-11 fiberglass insulation and wrap it around the valve or backflow preventer. (Crumpled up newspaper will also work for emergency insulation!) Then place a heavy duty plastic trash bag over the whole thing to keep it dry and use duct tape to hold it all in place. (For a more permanent installation you may want to use heavier plastic than a trash bag!) Don't seal the bag tightly, allow for an air passage at the bottom so water can run out and air can flow in! Just wrap it tight enough to keep the bag and insulation from blowing off. Insulation will not work if it gets wet! You can also buy ready-made insulation blankets for your valves and backflow preventers at most sprinkler supply stores. (You may need to special order them.) These consist of a large bag made from fiberglass filler sandwiched between soft vinyl cloth, much like a sleeping bag. This insulated bag goes over the backflow preventer and ties or padlocks in place. One brand that I have used is "Polar Parka". They get a free plug because they sent me a small sample insulation bag, about the size of a bed pillow! I carry it in my truck where I use it as an emergency pillow, a hand warmer, or a great place to put six-packs of soda to keep them cold during the summer!

    5. Now you need to remove the water from the pipes and sprinklers so that it won't freeze and break the pipe. There are two ways to do this, drain the water out through drain valves, blow it out using air, you can even suck it out sometimes with a shop vacuum (that's a lot of work though, you'll have to empty the shop vac over, and over, and over...!). Blowing out the system is the best method to use. I will detail how to do both blow the system and/or drain it, but I want to stress that blowing out the water is not a project I would recommend attempting for the average homeowner. I recommend that you hire a professional to do it for you. If you don't want to pay someone to blow the water out, then install drain valves and use the drain valve method below!

      Drain Valves:
      • In order to properly drain out your irrigation pipes you need to have drain valves installed at the appropriate locations. This means you will need at least one drain valve upstream of the valves, and one drain valve downstream of each valve. Note that you can't legally install a drain valve upstream of the backflow preventer(s). The reason for this is that the drain valve creates a point at which contaminates can enter the pipe, and there is no backflow preventer to keep them out of the drinking water supply. That means if you are using anti-siphon valves or atmospheric vacuum breakers you will not be able to have a drain valve on your mainline! Normally you will want to install the mainline deep enough that it will not freeze. Remember- your mainline between the water source and the backflow preventer must comply with all codes that relate to potable water (a fancy term for drinking water) lines. If you are really lucky you can install the mainline so that it slopes down to the vacuum breakers and will drain itself if you remove them. In some areas you may not even be allowed to drain them out through the open pipe end as there is a small possibility that this could also allow contaminates into the pipe. Drain valves can either be manually operated (you open the valve before the first hard freeze) or they can be automatic.

      • Remember three important things. First, you need a drain valve at EACH low point in the piping- despite what you may have seen at the amusement park mystery house, water will not flow uphill! Second, if there is not a sprinkler at the high points in the piping you will also need a valve at the high point to let in air. The water won't flow out unless air can get in! The final thing to remember is that if you use manual drain valves you're going to need to get to the valve to open it- and it's probably going to be cold and miserable on the day you decide the irrigation system needs to be winterized! So put the valves in a nice, big, easily accessible box and write down the locations of all the valves so you know where to look for them. When it's snowing outside you don't want to have to go hunting for the drain valves! You need about 1/4" per foot of slope to drain the pipes efficiently. If you work it right you will only need a single drain valve for each lateral. Most installers will try to install the pipe so that the lowest point in the circuit is just after the remote control valve. From there the pipe slopes up to the sprinkler heads. That way you can install the drain valve at the same location as the control valve, and they will both be easy to locate and winterize. Then you install a large valve box over both the control and drain valve. It's also a good idea to dig a 12" diameter pit, 24" deep under each drain valve and fill it with gravel. Then when you release that extremely cold water out of the pipes it has somewhere to go besides up your shirt sleeves and pant legs!

      • Automatic drain valves. Automatic drain valves open by themselves each time the pressure drops in the pipe. So at the end of each irrigation cycle the automatic drain valves will open and the water left in the pipes will drain out. Sounds good, right? Well it is and it isn't. The problem is that automatic drain valves tend to stick closed if they don't have a chance to open regularly. So if you use one upstream of a valve (on the mainline) it will stay closed during the entire irrigation season (because you keep the mainline pressurized all the time) and will likely stick closed when you turn off the water at the end of the season! Thus, even if you choose to use automatic drain valves you should still install manual drain valves on the mainlines. Downstream of the valves on the lateral pipes sticking isn't a big problem because the automatic drain valves get a chance to open after each irrigation cycle when the pressure drops. But that also means that all the water drains out of the pipes at the end of each irrigation cycle, every time you run the sprinklers, all season long! I don't like that, because it creates two problems. The first is that it wastes water. The second is that refilling with water after each irrigation is tough on the piping. Have you noticed spewing, spitting, and banging noises when air comes out of the sprinklers? That's the water slamming into each of the ells and tees in the piping as it fills the pipe! And that is NOT good for the pipe or the sprinklers. A few times a year is one thing, but every time you run the sprinklers...? So I recommend manual drain valves for most people. Now, are you the forgetful type or a procrastinator of the worst kind? Yeah, you know who you are! In that case use the automatic drains. The wear and tear caused by the automatic drain valves is less expensive than replacing pipes that broke in a freeze.

      • The water will not drain completely out of the valves. You will need to either completely disassemble and dry out the valves or remove them and store them inside. I suggest removing and storing them and disassembling them can get you into big trouble if you don't know exactly what you're doing. Removing them can be pretty easy if you install unions or other specialized devices on them that make them easier to remove. Ask a sprinkler supplier about these or look in the installation tutorial. Don't forget to cap the pipe ends where they connected to the valves after you remove the valves to keep garbage and critters out of the empty pipes!

      • Some sprinkler heads must also be drained out because water becomes trapped in them. This is common among sprinklers with built-in check valves, such as many better quality pop-up rotors have. Also heads installed using the inlets on the side of the sprinkler body (called side inlets) will not drain by themselves. I don't recommend using side inlets when installing sprinklers as they cause a number of maintenance problems, this being just one. If you're not sure if you have this type of sprinkler, remove the cap from one of them and see if there is water trapped down in the sprinkler body. If so you need to get the water out of there, which may mean removing the sprinkler and shaking it out! Or try vacuuming it out with a wet/dry shop vac. For sprinklers with side inlets you can install an automatic drain valve in the bottom inlet of each one so they will drain by themselves, but this gets pretty expensive. Since draining out these types of sprinklers is a lot of work you would probably be better off just paying a professional to winterize your system for you by blowing it out as described below.

        Drain away those freeze damage sorrows!


      The Blow-Out method:
      • This is not a method I recommend for amateurs! It is not a project for the average "do-it-yourselfer". Almost all big sprinkler systems such as golf courses and parks are winterized using compressed air. But one tiny little mistake-- and you will no longer own a sprinkler system. You will now be the proud owner of a bunch of buried plastic shards! So I recommend leaving this method to the professionals. If you try it and one of your sprinklers is launched like a bottle rocket, don't come crying to me!

      • In order to blow the water out of the pipes you will need an air compressor, and it can't be just any air compressor! It needs to be a big, BIG air compressor. Probably bigger than that compressor you already own. In other words that high pressure, low volume compressor you use in the shop is not the right compressor to use! (Did I mention this isn't a project for the average do-it-yourselfer?) How big you ask? For a really small irrigation system (3/4" PVC pipe or 1" poly pipe) you will need at least a 20 cubic feet per minute air compressor. And that is so small that it is not going to do a very good job! Most experts recommend nothing smaller than a 50 cubic feet per minute compressor for a home sprinkler system. Professionals often use a large gas or diesel powered compressor that can discharge over 125 cubic feet per minute of air and can blow out a pipe as large as 3" diameter. For pipes over 4" they use a 250 cubic feet per minute compressor. Note: SCFM means "Standard Cubic Feet per Minute" and for our purposes here, it's the same thing as CFM. SCFM is a measure of CFM at a specific temperature and altitude.

      • Here's what you should NEVER use. Do not use an air tank filled with compressed air or gas. Do not attempt to create more air flow by filling an air tank, then attempting to blow out the system with large bursts of air from the tank. Do not try to connect the exhaust pipe of your car (truck, boat, cow) up to the sprinkler system. Do not try to use a leaf blower or a vacuum cleaner with the flow reversed. Forget about using your electric tire pump (most of them have a hard enough time just inflating a tire!).

      • Each sprinkler system is different. I strongly suggest renting an air compressor rather than buying one until you have found an air volume that works well for you. Many variables effect the proper selection including local altitude, temperature, and type of pipe. Besides, it's probably a whole lot cheaper to rent one once a year.

      • Start by removing the backflow preventer (for anti-siphon valves remove the whole valve). Hopefully the backflow preventer is installed right after the irrigation shut off valve where your irrigation system taps into the water supply. If it isn't you're in trouble. You could install a blow out fitting (usually a tee with a 1" side outlet, and a short length of pipe with a threaded cap on it) for connecting the compressor up to right after that shut off valve. Unfortunately, in most places you can't legally install a blow out fitting upstream of the backflow preventer(s). The reason for this rule is to protect against the possibility of some idiot hooking up some piece of equipment to the blow out fitting that would allow a pollutant to get into the pipe. Once in the pipe the polutant could then be sucked into everyone's water supply (there's no backflow preventer to stop it upstream of the backflow preventer! OK, sorry, I know you're not stupid, and I didn't need to explain that.) Now, come on you say, what's going to be hooked up to it that would pollute the water? Well, a good example would be an air compressor. (Opps... !) When you blow out that pipe out you are blowing more than air in, you are also blowing compressor oil into the pipe! Yuck. So if you do decide to go ahead and blow out the pipes upstream of the backflow preventer, and your family all come down with a bad case of the trots the next day don't say I didn't warn you! (Nothing like a little compressor oil to lubricate the old human plumbing system.) Fortunately, if your irrigation system is installed correctly you shouldn't need to blow out the mainline upstream of the backflow preventer! Allow me to explain (like you have a choice!). The mainline between the water source and the backflow preventer is supposed to be installed in compliance with all codes that relate to potable water pipes (potable is a fancy term for drinking water). One of the requirements found in most plumbing codes is that potable water lines must be installed below the frost line to keep them from freezing, or some other method must be incorporated in the design to prevent freezing (such as a pipe heater). If your mainline upstream of the backflow preventer isn't designed not to freeze, see if you can figure out some way to drain the mainline (see the drain valve section above). If that won't work you may need to reinstall the pipe deeper, or install a pipe heater. Another option is to relocate the backflow preventer so that it is right after the irrigation shut-off valve so there isn't any mainline upstream of the backflow preventer. For more information on backflow preventer types to use see the backflow preventer page.

      • Next, connect the air compressor to the backflow preventer riser (on the downstream side). Do not blow air through the backflow preventer or through a pump, you could damage them! It is important that the air compressor has a pressure regulator valve with an accurate gauge on it. Do not turn on the compressor yet! If you have anti-siphon valves you'll skip this step (but don't skip the warnings!).

      • Safety first! Plastic pipe is not designed to hold compressed air! Air does not behave the same way as water in a confined space. Weird and unexpected things happen! Put on eye protection and keep everyone away from the sprinkler heads. If the air becomes trapped by a pocket of water in the pipes it can suddenly "burp" free with enough force to explode the sprinkler heads! Always increase the air pressure in the pipes slowly. Never attempt to blast out the water with a sudden burst of air. If you can't get the water out with a steady flow of air, then you need a higher capacity air compressor.

      • Using the automatic controller (timer), turn on the last valve that is furthest from the backflow preventer. Only turn on one valve at a time! If one valve is considerably higher in elevation than the others you may want to start with it rather than the last valve. But in most cases the last valve is the first one you should blow out. If you have manual valves just open the valve manually. If you have anti-siphon valves (which you removed earlier), you will not be able to open the valve (because you removed it?) So instead you will now need to hook the compressor hose up to the downstream side of one of the valve risers.

      • Turn on the compressor and slowly increase the pressure. Carefully monitor the air pressure, never allowing the pressure in the irrigation system to exceed 50 PSI! You probably won't even need 50 PSI to blow out all the water. The lower you can keep the pressure, the better. Watch the temperature also! Air heats up as it is compressed (physics 101). The air can be very hot when it leaves the air compressor, hot enough to melt the plastic sprinkler pipe! It may be necessary to add some extra length of hose between the compressor and the connection to the sprinkler system so the air can cool a bit before entering the sprinkler system piping.

      • Allow the air to run until all the water is blown out and only air is exiting through the sprinkler heads. Don't blow air through the system any longer than necessary. If it takes more than 2-3 minutes for the water to get out, stop the compressor and let everything cool down for a few minutes, then start again. Be patient! Keep watching that pressure and temperature! The first valve will probably take a lot longer to blow out than the others because most of the water in the mainline pipes gets blown out of the first valve zone.

      • After only air is coming out of the sprinklers, turn off the air compressor, and then turn off the valve. Open the next valve, turn back on the compressor and repeat the blow-out procedure. Continue until all the valve circuits have been blown out. Note that if you have anti-siphon valves you will need to switch the compressor hose to the next valve riser.

      • Never turn off all of the valves while the compressor is still running! A valve must be open at all times. The goal is to blow OUT the sprinklers not blow UP the sprinklers!

      • When all the valves have been blown out it is a good idea to repeat the entire process again, starting with the first valve.

      • If you have a mainline section upstream of the backflow preventer that you are planning to blow the water out of, nows the time. Hook up the compressor to the blow out fitting just downstream from the irrigation system shut-off valve and blow the water out through the backflow preventer riser. Set out the Pepto-Bismol where the family can get to it easily!

      • Put the automatic controller into "rain mode" when you're finished blowing the system out. (Or you can turn it off if you wish.) Install threaded caps over the open ends of the backflow preventer risers, anti-siphon valve risers, and any blow out fittings to keep garbage and critters out until spring. Store the backflow preventer inside for the winter.

Spring start up procedures.

This is just as important as winterization, but nobody ever asks me about it! When you first turn on your sprinkler or drip system in spring you should always flush it out. During the winter many small critters take up residence in your sprinklers, emitters, tubes, and pipes. Often they manage to squeeze in, only to be unable to get back out when spring comes. Whether they crawl down to a smaller pipe and get wedged, or grow, or whatever, I don't know. But I do know they get in there and they get stuck! So you need to get them out. To do that open the ends of drip tubes and flush 'em out by turning on the water. For sprinklers remove the nozzles from, at the least, the last head on each pipe (better yet, remove them all) and run the water. When you think the water has run long enough, you're only half way done. Let it run twice that long! The biggest mistake in flushing is not letting the water run long enough. When done, make sure that standing water doesn't drain back into the pipes, taking dirt back in with it! You may need to put a temporary piece of hose or pipe onto the flush outlet to drain the water to a different area. Make sure the hose is as big or bigger than the pipe, you don't want to restrict the flow!

After flushing, check the system out by running it. Look for clogged emitters or nozzles. I don't recommend cleaning plastic sprinkler nozzles, replace them with new ones. Cleaning them leaves small scratches which mess up the spray pattern and create dry spots. (So that's why you have more and more dry spots each year! Who would have known! And you thought using that screwdriver to pry out the sand grains was a brilliant idea!) Calcium buildup on sprinkler nozzles can be removed using one of the many calcium remover products available for kitchen use. I've never tried it but I've been told that soaking them in drain clog remover also works. If you try it let me know if it works!

Check for leaking valves. Often the flexible seals dry out over the winter and leak when the water is turned back on. This is also a good time to think about giving your plants some fertilizer. They just woke up from a long nap and they're HUNGRY! Did you miss Little Shop of Horrors? Feed them, but not too much!

Check the controller for proper run times for each station. If it has a back-up battery replace it with a fresh one. Almost all solid state controllers use ALKALINE back-up batteries and will not work right with other kinds- if in doubt use an alkaline type battery. The battery on some controllers is located behind a face plate where you can't see it (why do the manufacturers do stupid things like that?), so if you don't see a battery, remove the wiring compartment cover and look for it in there. A few of the high-end controllers have built in battery chargers (look at the batteries, they should be labeled "rechargeable" if the clock has a built in charger). Most newer controllers now come with non-volatile program memory and long-lasting batteries to keep the clock running during a power outage. These batteries are like the ones in your computer, they last for years, you may never need to change them.

If you have a sprinkler system, give it a spring tune-up. See the Sprinkler System Tune-Up instructions.

Special thanks to the following industry experts who provided input for this tutorial! (I admit it! We don't do much winterizing here in Southern California and I needed all the help I could get!) The following list is in random order.