Shutting off the irrigation system for the winter season

Shutting off the irrigation system for the winter season

In cities where frosts may occur during the winter season, the irrigation system must be emptied and prepared for the winter, through a process known as winterisation. Particular attention should thus be paid to flushing out any water from the pipes, valves and sprinkler heads: here you can find all the information that you may need to shut off the irrigation system.

Manual drain valve installed on the main pipe

A manual drain valve should be installed on the mainline of the irrigation system, at the lowest point. If there are multiple low points along the route of the pipe, in which water may accumulate, additional manual drainage valves should be installed.

For the actual drainage, it is possible to utilise a ball valve or gate valve or even a simple pipe with cap. The pipes must also be inclined correctly to allow the water to drain out. If the valve is located outdoors, it must be installed inside a dry well (underground and filled with gravel to drain water from the pipes) to allow the amount of discharged water to filter into the ground. If the valve is installed in a technical room, it is necessary to ensure that the volume of water can be collected or discharged without the risk of overflow or flooding. Both the manual drain valve and drain plug are under pressure before winter drainage and could cause physical injury if opened without due care. For this reason, it is necessary to wear adequate eye protection

  • Turn off the shut-off valve on the main line of the irrigation system.
  • Open one of the solenoid valves (manually or electronically via the control unit) to release the pressure of the irrigation system’s main line.
  • Open the manual drain valve.
  • Repeat this procedure for all manual drain valves on the irrigation system’s main line.

Automatic drain valve

Automatic drain valves should never be installed on the mainline (that upstream of the solenoid valves). An automatic drain valve is a spring-loaded device installed on hoses or sprinkler heads. It is an economical and efficient product for evacuating water from the lateral piping network (piping downstream of the solenoid valve) that goes from the irrigation system control valves to the heads. Automatic drains must be installed on the lateral piping network (piping downstream of the solenoid valves).

The drain valve will open each time the system is turned off. This will drain all the water from the pipe, provided that the valve is installed in the correct position (being the lowest point on the line). When the system is under pressure, the water closes the valve by pressing against the sealing mechanism, allowing the water to properly flow through the hose and sprinklers.

One or two drains is all that is needed to complete the operation. Drain valves usually have ½” or ¾” threads. The drain valve must be connected to the pipe with a threaded fitting and installed facing downwards. If the soil has poor drainage, it is advisable to remove the soil near the drain and replace it with draining material

  • Automatic drain valves remove water from the system every time it is turned off. 
  • No manual operation should be required
  • Periodically check for excessive pools of water on the surface of the soil (indicating blocked drains during sprinkler operation).

Emptying the system with compressed air

To empty the system with compressed air, wear suitable Personal Protective Equipment (and eye protection in particular). Pay special attention to any excessive pressure that could damage the sprinkler hose or valves or even cause physical injury (flying debris). For this procedure, it is recommended to turn to a professional who is fully equipped to provide this service.

When expelling air, proper distance should be kept from installation components, such as the pipes, valves and sprinklers. The air pressure should not exceed 3.5 bar. Compressed air is utilised to push water through all components of the irrigation system, including the pipe of the mainline, the sprinkler control valves, lateral pipes and sprinkler heads. To obtain an adequate air volume, it is necessary to rent or purchase a compressor that can provide from 280 to 700 litres/minute in air volume. The air pressure should not exceed 3.5 bar during the blowout procedure. It is necessary to use a pressure-regulating valve to avoid overpressure in the system. The air volume should be high whilst the air pressure should be low: this combination of high volume and low pressure will minimise any damage that could occur during the wintering process.

How to empty the system with compressed air

  • Close the shut-off valve of the main line.
  • Discharge the water pressure from the main line by activating a solenoid valve via the timer. 
  • Before introducing air into the pipeline, activate the solenoid valve farthest from the connection between the system and air inlet of the air compressor.
  • Connect the compressor hose to the drain adapter.
  • Set the pressure control valve on the compressor to 3.5 bar.
  • Turn on the compressor. Gradually increase the air flow until the sprinkler heads rise. The amount of flow or volume required will depend on the length of the pipe and the number of heads.
  • The heat generated by compressed air can damage the hose and other components. Do not blow air into any circuit for more than 2 minutes at a time. Switch to another zone (solenoid valve) by stopping the manual start via the timer then moving on to the successive zone. Never turn off the timer during this operation unless the compressor is already switched off.
  • In order to ensure adequate drainage of the lines, repeat the cycle two or more times, activating each zone via the timer, until the discharge of water spray is more visible from the heads. Many sprinklers that use plastic gears in their drive mechanisms also utilise water for lubrication and cooling. If a circuit is allowed to operate only with air for prolonged periods, there is a significant risk of damaging the sprinkler drive mechanism.
  • After turning off all zones, leave one area on whilst turning off the compressor. Only then can the compressor be switched off.
  • Disconnect the compressor from the adapter to the main line of the irrigation system.
  • Turn the timer to “OFF”.

Cleaning the solenoid valves

Use gravity to empty the aforementioned system does not eject the water trapped within the solenoid valves. For valves that are not emptied with compressed air, this is the procedure that must be followed:

  • remove the upper body, the solenoid and the solenoid valve membrane.
  • drain the stagnant water.
  • next, replace the solenoid valve, leaving the solenoid in the open position for the winter.

Control units with tap

If the irrigation system has a Control Unit with Tap (Amico+, Amico+2, Amico R, Amico R2, etc.), then this must be stored in a sheltered location.

  • Manually turn off the tap on which the programmer is installed.
  • Remove the programmer from the tap.
  • Set the programmer to “OFF”.
  • Store the programmer in a frost-protected and dry location.

IP-68 valve box control units

If the irrigation system has a valve box control unit (Amico Pro, Pure Vision, etc.), then this must be stored in a covered location.

  • Disconnect the control unit from the quick connectors for 9vDC solenoid valves.
  • Remove the programmer from the valve box.
  • Set the programmer to “OFF” to retain the programming.
  • Store the programmer in a covered and dry location.

Indoor control units

If the irrigation system has an indoor control unit (I-Dial, C-Dial, Elite, etc.):

  • disconnect the timer: please note that turning off the timer via the switch does not guarantee complete safety when turning the timer back on in the event of an overvoltage or power failure.
  • the models turned off by the switch (timer in the OFF position) can be easily reactivated. The indoor models have a power cord connected to a transformer. Simply disconnect the transformer from the power source – the transformer may be hot and should be handled with gloves to avoid burns.
  • removing the backup battery results in the loss of programming data, hence programming will have to be reset in the spring.

Outdoor control units

If the irrigation system has an outdoor control unit (I-Dial, C-Dial, Elite, s-Dial, etc.), then this must be stored in covered location.

  • Disconnect the timer: please note that turning off the timer via the switch does not guarantee complete safety when turning the timer back on in the event of an overvoltage or power failure. The models turned off by the switch (timer in the OFF position) can be easily reactivated. 
  • In outdoor control units, the cables pass through the conduit and connect the power supply with the control unit (which is equipped with an internal transformer). Touching high-voltage cables can result in electric shock and burns. Do not attempt to disconnect these wires to turn off the timer
  • The power supply can only be turned off from the switch panel of the main grid. If you decide to remove the buffer battery, check that the power is completely off.
  • Removing the buffer battery results in the loss of programming data, hence the programming will have to be reset in the spring.