Protect the investment you have made in your drip irrigation system by protecting it from winter damage.
Drip irrigation systems all use valves, filters, plastic fittings, PVC pipe, poly pipe, or layflat hoses that can easily burst if water freezes inside any of these components. I know this from personal experience and it can drive you crazy. This can prove costly to replace or repair.
Winterizing a drip irrigation system will take between fifteen minutes to an hour, and is best done before the first freeze. The little time spent now will result in a low maintenance irrigation system that does not need replacement parts because of freeze damage. In extremely cold winters, freezing temperatures can severely damage your irrigation system and all the main water lines.
The goal in winterizing your drip irrigation system is to shut off the water supply to the system, and flush all of the water that is left in the system from the backflow device, valves, filters, main lines, sub-lateral lines, sprinklers, drippers, and drip line. One way to make sure that the system will not freeze (flat terrain) is to install automatic drain valves in the lowest point of the system. The drain valve assures that any water in the line will drain out. This is extremely important. Also in a drip irrigation system, I like to run some chlorine (2 PPM) through the system and then flush it out thoroughly to clean everything up before storing it for the winter. That way it is ready to be used again next year.
About the parts of the irrigation system:
Always drain a pump by opening the lowest plug or drain outlet (replace with drain valve). Make sure to check that no water is left inside. Drain plugs usually are extremely difficult to remove, not to mention difficult to get to, making an unpleasant project out of a simple task. For some of our portable drip irrigation trailer units (engine and pump located on a trailer) and with drip irrigation systems fed from a pond or a stream, drain the suction line. That is pull it out of the water, drain it and cover the open ends to prevent creatures from making it a winter home. Also the open end of the pump where the suction line connects needs to be covered so that rocks, pebbles, nutshells, leaves, and animals from mice to snakes can find their way into the impeller. Simply covering open ends will save time and headaches.
Valves and valve assembly
Gate and ball valves will not tolerate freezing. A gate valve, when closed, traps water in the bonnet. A ball valve holds water inside the ball. If the valve is closed when water is in the line and the line is drained without opening this valve, the water trapped above the gate or inside the ball will freeze and have no place to expand. The signs of freezing are very distinctive: a ball valve will burst the side out, and a gate valve will split its bonnet, packing nut, or have a hairline crack down its side. Replacing a three-inch brass gate valve is not cheap.
Solenoid valves are best winterized by leaving them open for the winter. The manual bleed lever on the valves varies by model and manufacturer, but is usually a thumb type screw on top of the valve or lever on the side of the bonnet (cover).
Automatic control valves such as pressure reducing, pressure relief or combination valves, containing external control tubing, pilots, and other parts will require special care to thoroughly drain. If the entire unit can be easily removed from the pipe, I would recommend storing the unit in an inside location for the winter. This is the method that I prefer after years of winterizing systems. If removing the valve or valve assembly is not practical, then from the pressure-reducing valve remove the control tubing connections in the lower part of the valve to drain all the parts of water. The valve bonnet should also be loosened or removed to remove all the water from the top of the diaphragm by loosening the screws on the top of the bonnet.
Valve assemblies such as battery operated controllers or AC valves with filter, pressure regulator, and swivel adapter; also require special care to thoroughly drain. If the entire assembly can be easily removed from the pipe, it may be simple to store the assembly unit from the controller to the pressure regulator in an inside location for the winter. If removing the filter assembly or valve assembly is not practical, the valve bonnet should be loosened or removed to remove all the water from the top of the diaphragm, the filter cap should be removed from the filter, and remove the filter cover and screen to make sure that no water is left inside any part of the assembly.
First disconnect the drip tape from the laterals and in most cases it is disposed of as it is considered an annual expensed item. When Plastofuel finally becomes a reality it will become a feedstock for Plastofuel, which is then burned at 2000oF and will create electricity.
Poly pipe hose and vinyl layflat hose
Poly pipe and layflat hose have to be drained. Layflat or poly pipe hose can be lifted a few feet at a time and section-by-section, making sure that any water left in the hose will drain out. After you finish draining the layflat hose or poly pipe hose and the micro tubing or connectors, make sure to close the ends of the hoses using the hose ends. The layflat hose definitely is easier to roll up than the poly pipe hose, and can even be automated on a spool.
The best prevention I have found once the system is drained completely is to take those parts of the system that are prone to damage inside a building. At the Penn State Horticulture Research Farm we use trailer mounted portable pumping and filtering units, which can be drained and then moved into a building for storage during the winter. The vinyl layflat hose or poly pipe hose with connectors is cleaned up, rolled up and stored so the mice and rodents will not bother it. With proper winterizing of your irrigation system, you can relax and stay warm by the woodstove and know that your irrigation system is ready for use again in the spring.