October
2006
Blowing Out Your Sprinklers
If you live in an area of the world where the tempurature is going to get below the freezing point of water for any amount of time during the winter, about now you need to be thinking about blowing out your sprinklers if you haven’t already.
You system may have line drains in it, which helps drain the water from your lines after each cycle of watering, but often this will not be enough, especially where it gets really cold in the winter. Line drains should be at the low points of you system if you have it to drain any water and avoid freezing inside the lines, but often some water may not all drain, or if you hook up your sprinkler heads from a side port, the bottom of the sprinkler will still have water that needs to be removed.
Blowing out your sprinkler system will involve using an air compressor with compressed air in place of water in your system to remove all the water out of the lines. When choosing an air compressor, you want one that can put out at least 10 cubic feet per minute, and can reach 50 psi. 50 psi is probably the maximum pressure you would want to use when blowing out your sprinklers. Your water pressure may be a little higher, but components usually do not tolerate the higher pressure of air as well as water since they are a different density. The minimum cubic feet per minute is just as important as the pressure. When you blow out each zone, you need a compressor that has the horse power or has a tank that can maintain the 50 psi pressure while blowing them out for a minute or two.
When I winterize my sprinkler system and blow out my lines I will connect the air compressor to a designated place as far up the line as possible, closest to the water source. When installing the system I will add a “T” to connect the air compressor fitting before my backflow valve. This allows me to use the air just as I would the water in the procedure to blow out the lines. Here are the steps I follow each fall to blow out my sprinkler system:
- Turn off your water source to the system, and go to your timer or manually open each valve for about 15-20 seconds to drain the pressure.
- Use what adapters you need to connect your air compressor hose to your sprinkler system, and a minimum before your control valves.
- Make sure all the valves are closed and turn on the pressure from you air compressor. This should pressurize your system just as the water would. If you have an above ground backflow preventor, it may make some noise as it tries to seal the main valve. You may need to help it a little with your finger if you can.
- Now go to your timer or to the valve manifold for each of the zones and turn on one zone. The sprinkler heads should pop up just like they would with water, and start spraying out water until it empties the line. Then it should start sputtering with air and water and eventually just air. If you compressor can’t maintain the volume of air you may have to close the valve and let the pressure and air volume build up in the tank again.
- Repeat this procedure with each valve (zone) until all the lines for all the zones have been blown out. Usually I will cycle through each zone 2-3 times to make sure they are dry.
- You can now unhook your air compressor, leave all the valves open, keep your timer plugged in and turn it to the “Off” setting so it won’t run the valves during the winter. Also be sure to leave your main water for the system off. This seems obvious but I thought I would mention it. If you turn the water back on, go back to step #1.
You can often find local landscape companies that will come out and winterize your sprinkler system and blow out your lines for you, and usually they will add you to the schedule to turn it back on in the Spring. This might not be a bad idea if you are uncomfortable with this procedure, and may not be much more than the rental of an air compressor.