Every year, before the first freeze, the ritual of lawn irrigation “blow out” becomes the priority for all irrigation systems in New Jersey. Irrigation winterization is extremely important since the frost level can extend up to 24” below the depth of installed piping, which means your pipes can crack and break if any water is left inside.
To minimize the risk of freeze damage, you’ll need to winterize your irrigation system. Most systems installed in New Jersey require forced air to complete this process.
Winterizing a Sprinkler System in New Jersey
The blow out method for your irrigation system 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. The compressor is first attached to the mainline via either a quick coupler, hose bib or other type of connection which is located where the piping exits the building and near the backflow device.
To start the winterization blow out, shut off the irrigation water supply and turn on a zone by the controller to eliminate any pressure in the sprinkler system. Open the connection to allow any water to drain out of the backflow device and the piping from the building. Then, with the compressor valve in the closed position, attach the air compressor hose to the blow out fitting. Next, slowly open the valve on the compressor; this should gradually introduce air into the irrigation system. The blow out pressure should remain less than the maximum operating pressure for the component with the lowest pressure rating on that zone and should NEVER exceed 80 PSI.
Each station/zone should be activated, slowly working your way around the property. Each station/zone should be activated until no water can be seen exiting the heads; this should take approximately two minutes or more per station/zone. It is better to use two or three short cycles per station/zone than to have one long cycle.
Once the station/zone is dry, you should not continue to blow air through the piping. Compressed air moving through dry pipes can cause friction, which will create heat and could cause damage. Never run the compressor without at least one irrigation control valve open.
When every station/zone is empty, turn the air off and allow the system to depressurize. When complete, the air hose can be disconnected. BE CAREFUL. If there is still air in the system, it can cause the hose to whip around dangerously. Re-install the blow out connection fitting. Any ball valves on the backflow device should be put into a half on, half off position. This will keep them from building up moisture inside the valve and cracking the brass.
Caution: a small shop compressor (1-3 HP) will not have enough “free” air to properly winterize your irrigation system. Do not attempt to fully charge the holding tank then release the highly pressurized air flow into the mainline to compensate for the compressor’s lack of CFM. A compressor with enough “free” air will create a wall behind the water continuously until the water exits through the sprinkler heads. With a small shop compressor, once the initial burst runs out, the water will settle in the pipe and allow the air to travel over the water. This will leave a dangerous amount of water in the piping.
WARNING! Wear ANSI-approved safety eye protection! Extreme care must always be taken when blowing out an irrigation system with compressed air. Compressed air can cause serious injury, including serious eye injury, from flying debris. Always wear ANSI approved safety eye protection and do not stand over any irrigation components (pipes, sprinklers, and valves) during air blow out. Serious personal injury may result if you do not proceed as recommended! It is best for a qualified licensed irrigation contractor to perform this type of winterization method.
Due to the potential dangers involved with winterization, it is best to call a irrigation maintenance company.