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You are here: Home > Sprinkler School™ > Sprinkler System Basics > Winterizing Your Irrigation System > How To Blow Out Water

HOW TO BLOW WATER OUT OF THE LINES USING COMPRESSED AIR

CAUTION! WEAR PROPER EYE PROTECTION! Extreme care must be taken when blowing out the system to avoid excessive pressure which can damage valves or sprinkler pipe or cause physical injury due to flying debris. Do not stand over any irrigation components (pipes, sprinklers, and valves) during air blow out. Air pressure must not exceed 50 pounds per square inch (psi) for systems with polyethylene piping, and 80 psi for systems with PVC piping.

Local irrigation contractors usually offer this service for a reasonable fee which may also include start-up in the Spring. Depending on how extensive your system is and what type of equipment you have installed, you may want to choose a professional who is fully equipped to provide this service. 

The blow out method utilizes an air compressor with a Cubic Foot per Minute (CFM) rating of 80-100 for any mainline of 2" or less. These types of compressors can be rented at your local equipment rental yard.

Description: Compressed air is used to force water through all of the irrigation system components including the mainline pipe, sprinkler control valves, lateral pipes, and out through the sprinkler heads. To obtain proper air volume, you will need to rent or buy a compressor capable of providing 80 to 100 cubic feet per minute (CFM) of air volume. During the blow out procedure, the air pressure must not exceed 50 pounds per square inch (psi) for poly pipe system or 80 psi for PVC pipe systems . A pressure regulating valve must be used to avoid over pressurization of the system. Air volume should be high and air pressure low. This combination of high volume and low pressure will minimize the damage that can occur during the winterization process. It is very important to select the right air compressor for the job. Some small shop compressors (2 hp) may not be adequate to complete the winterization procedure properly.

If the appropriate air compressor is not available, please call an irrigation contractor. Do not try to use an air compressor with high pressure (120 psi) and low volume to evacuate water from the system. It is not an acceptable practice to allow the compressor to fill the holding tank of the compressor and the closed mainline with high pressure air, hoping the surge of excess pressure will compensate for the lack of compressor size and blow the line clean upon opening the sprinkler control valve. This is a dangerous practice that places very severe stresses on all of the components of the system. Do not run the compressor without at least one sprinkler control valve open. This lessens the chance that the system could over pressurize. It is a common misbelief that if the system can withstand 120 psi of water pressure, similar air pressure will not damage the system. This is not true! The viscosity of air is much lower than water, generating much higher stresses that can cause severe damage to the system.

Design: There should be a separate provision on the sprinkler system mainline for hooking up the air hose (see item C in the diagram). This could be a quick connect fitting, a hose bib, a manual gate valve, a plugged "tee", or simply a capped pipe in the line. This adapter should be located as close to the water source as possible, but should be located after the backflow device. Compressed air should not be blown through any backflow device. Check with your air compressor manufacturer for the correct procedure and equipment to hook up to the sprinkler system.

 

 


Blow out procedure activating valves Automatically

Procedure: Wear Proper Eye Protection! Do not stand over any irrigation components (pipe, valves, or sprinklers) during air blow out. Do not run the air compressor without a sprinkler zone control valve being open first, from start up to compressor shut down. Air pressure must not exceed 50 pounds per square inch (psi) for poly pipe systems and 80 psi for PVC pipe systems.

Blow out procedure activating sprinkler control valves from the timer:

  1. Close mainline sprinkler shutoff valve. ( A )

  2. Relieve the water pressure on the mainline by activating a circuit, or zone, from your timer. Activate the circuit that is furthest from the air connection before introducing air into the piping.

  3. Attach the compressor hose to the blow out adapter. ( C )

  4. Set the pressure regulating valve on the compressor to 50 psi for poly pipe systems or 80 psi for PVC pipe systems.

  5. Turn on the compressor. Gradually increase the flow of air until the sprinkler heads pop up. The amount of flow or volume required will be dependent upon the length of the pipe run and the number of heads.

  6. Sustained heat from the compressed air may damage pipe and other components. Do not blow any circuit more than 2 minutes at a time. Switch to another station, or zone, by advancing the timer to the next circuit. Do not turn the timer off at any time during this operation until the compressor is first shut off.

  7. In order to ensure adequate drainage of lines, repeat the cycle two or more times, activating each zone from the timer, until nothing more than a fine mist appears from the heads. Many sprinklers that use plastic gears in their drive mechanisms also use water for lubrication and cooling. If a circuit is allowed to run with nothing but air for extended periods there is a significant risk of damaging the drive mechanism of the sprinkler.

  8. After blowing out all the zones, leave one zone on while shutting down the compressor. Turn the compressor off at this time.

  9. Unhook the compressor from the adapter to the sprinkler system mainline.

  10. Turn the timer to "Off".

Blow out procedure activating valves Manually

Use this section only if your system does not have electric remote control valves.

Procedure: Wear Proper Eye Protection!
Do not stand over any irrigation components (pipes, valves, or sprinklers) during air blow out. Do not run the air compressor without an irrigation control zone valve being open first, from start up to compressor shut down.

Please refer to Blow Out Procedure Activating Valves from Timer section before considering this alternative. Activating the valves from the timer offers an additional margin of safety to the procedure since you would not be placed in close proximity to the irrigation components during the blow out.

Blow out procedure activating valves manually:

  1. Close main sprinkler shutoff valve. ( A )

  2. Relieve the water pressure on the mainline by slowly opening the manual shutoff handle on one of your irrigation zone control valves.

  3. Attach the compressor hose to the blow out adapter. ( C )

  4. Set the pressure regulating valve on the compressor to 50 psi for poly pipe systems or 80 psi for PVC pipe systems.

  5. Turn on the irrigation station you want to blow out.

  6. Turn on the compressor. Gradually increase the flow of air from the compressor flow valve (not from the sprinkler control valve) until the sprinkler heads pop up. The amount of flow or volume required will be dependent upon the length of the pipe run and the number of heads.

  7. Sustained heat from the compressed air may damage pipe and other components. Do not blow any circuit more than 2 minutes at a time.

  8. After 2 minutes, turn the compressor off, and allow all of the air to completely purge from the compressor tank and the sprinkler system.

  9. Turn on the next irrigation control valve you wish to winterize.

  10. Turn off the last irrigation control valve you have just blown out.

  11. Repeat Steps 5 through 10 until you have completed 2 or more blow out cycles per zone. There should only be a fine mist blowing from each station if the winterization procedure was successful. Cycle again as needed.

  12. Turn the compressor off. Allow any air in the storage tank or irrigation components to disperse before approaching the air hose or valves.

  13. Unhook the compressor from the adapter to the sprinkler mainline.
 
   
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