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Winterizing Your Irrigation System

It is the time of year again to prepare your system for the winter. Please review this article to make sure that you follow all the steps necessary to avoid damage to your system. All sprinkler or drip systems that utilize valves, filters, plastic fittings, PVC pipe, poly pipe, or drip hoses can easily burst if water freezes inside any of these components. This can prove costly to replace or repair. The following steps should be taken to minimize the risk.

Winterizing a sprinkler or drip system will take about fifteen minutes to an hour, and is best done before the first freeze. A little of your time will result in a low maintenance irrigation system that will reduce the need for replacing frozen parts.

In extremely cold winters, freezing temperatures can severely damage your irrigation system and all the main water lines.

The goal in winterizing an 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. With automatic drain valves it is not necessary to blow out the sprinkler lines with compressed air. The drain valve assures that any water in the line will drain out.

Steps to take in early fall to assure an easy time in the spring:

  • Step 1: When freezing weather is anticipated, simply turn off your main water supply to the irrigation system and make sure that the backflow device, valves, filter, pressure regulator, pipe, sprinklers, drip hose, and drippers are free of water.
  • Step 2: After the main water supply is shut down, run the timer/ controller through its normal watering cycle. This will allow each of the valves to open and relieve water pressure on the main line and valves. Allow the lines to drain slightly. After the timer/controller runs through its cycles, turn the controller off, or to Rain Off position.
  • Step 3: The most important thing to do in very cold temperatures is to wrap all exposed pipe with insulating tape. The insulation should cover everything exposed up to the risers; however, it is unnecessary to wrap sprinkler heads or hose bibs.
  • Step 4: Through the height of winter leave the system off and drained. If needed, water your plants and lawns with a hose only. In most cases, there is enough moisture in the ground from rain to sustain the plants and lawns during the extreme winter periods.
  • 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.

    Along with the pump, drain the suction line. Pull it out of the water, drain it and cover the open pipes to prevent creatures from making it a winter home. Rocks, pebbles, nut shells, 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 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.

    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 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, it may be simple to store the unit in an inside location for the winter. If removing the valve or valve assembly is not practical, 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 un-tightening 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.

    Our recommendation: store the unit for the winter
    Drip hose
    First disconnect the drip hose from the filter assembly and make sure to wrap the swivel adapter or the connection to the filter assembly with a plastic bag to prevent dirt and contaminates from entering the drip tubing. If the drip hose is installed above the ground, open all the ends of the drip tubing and allow the water to drain. Then lift the drip hose from the connection of the filter assembly, a few feet at a time and section by section, making sure that any water left in the drip hose will drain out. After you finish draining the drip hose and the micro tubing, make sure to close the ends of the drip tubing using the hose ends
    PVC and poly pipe
    PVC and high density poly pipe have to be drained. Some systems have manual drain valves or automatic spring-loaded drain valves at the end line, but these may not be installed properly, or the ground may not be flat, or the drain valve may not be at the lowest spot; there is no guarantee that the pipes will be thoroughly drained. The only way to make sure, if the pipe is below the ground, is to use air pressure to blow out the system.

    When using an air compressor to blow out an irrigation system, use low pressure with high volume, maintaining at least 30 to 40 PSI, and do not exceed 50 PSI. One of the reasons for this is if the air velocity is too high, it will create heat friction that can cause damage to the pipe and other components of the system. Please use extreme caution when pushing compressed air into an irrigation system. Some manufacturers will not honor their warranties if their product is damaged by compressed air.

    Draining your system using an air compressor:

  • Open manual drain valves to allow for gravity to drain all water from main lines.
  • Shut off all manual valves and pressurize the system with compressed air (compressors can be rented from your local rental supply).
  • Turn on controller manually, and advance to each zone until heads blow air.
  • Repeat for each zone via the controller.
  • Leave all small brass and plastic valves "open" if double check valve is installed.
  • Do not use compressed air with a drip system.
  • Disconnect