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I cannot find a service in northern NJ to winterize my sprinkler system for less than $100, so I want to try doing it myself, I just don't want to break anything. I've watched a few youtube videos, but haven't quite found a system that looks like mine so I really want to be sure I'm doing this right. I know where/how to shut off the water to the system in my basement. I was planning to rent an air compressor from home depot. I'm just not sure where to hook it up, and which knobs to turn and when. Below is a picture of my system. I added numbers to make it easier to reference the different parts.

Sprinkler system

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You want to clear water from the system and the backflow valve. It looks like the hose bib is a tee off the irrigation feed with its own valve.

If there is no inside shut-off valve dedicated to what comes out of the wall, follow these instructions:

  1. Close valve 3 (turn perpendicular to the pipe).
  2. Leave valve 1 open (parallel with the pipe).
  3. Attach the compressor to port 4. Turn the port 4 screw 1/4 turn so it's parallel with that stem.
  4. Assuming you have an irrigation controller, cycle it through each zone for several minutes in each zone. A "test" cycle may be long enough. Water will spray from the irrigation heads, then it will turn to mist as the water is cleared out of the zone. You want to pressurize each zone until there's nothing but air coming out of the last head in the zone.
  5. When all of the zones are done, open port 2 (turn the screw 1/4 turn so it's parallel with that stem), and close valve 1. Give it a few seconds to empty any water in that stem.
  6. Remove the compressor from port 4.
  7. Open valve 1. Any pressure trapped in the system will escape through the open ports.
  8. Close the two ports by turning the port 2 and port 4 screws perpendicular to their stems.
  9. Leave valve 1 open and valve 3 closed (that will protect the backflow valve, which is expensive to replace).

You're done.

If there is a dedicated inside shut-off valve, follow these instructions, instead:

  1. Close the inside valve.
  2. Leave valve 3 open and open the port 4 valve. Open the valve on the hose bib. Close valve 1.
  3. Attach the compressor to port 4. Blow any water in the feed pipe out through the hose bib.
  4. Leave the hose bib valve open and complete steps 1 through 8 above (including closing valve 3 and reopening valve 1 in steps 1 and 2).
  5. Modified step 9: leave both valves 1 and 3 open.

BTW, you want a compressor with a lot of CFM or a large tank, but it doesn't need to be high pressure. The compressed air will drain pretty fast when you're blowing it out of open ports and lots of sprinkler heads.

  • This is awesome, thanks for the write up. It's still not clear to me if there is any urgency for turning off the compressor between steps 4 & 5. If I put the controller on test mode to cycle through each zone for 2 minutes, is it bad if test mode finishes and the compressor is still on? Wouldn't it be pressurizing a sealed system, making it very urgent to open port 2? Or should I just aim to turn off the compressor before test mode finishes on the last zone? Would that be bad either (having an active zone with no water and no air pressure? – JCB Nov 20 '17 at 0:22
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    @JCB, normal household water pressure is in the range of 60 PSI. If the pressure from the water utility is over 85 PSI, there is supposed to be a pressure regulator, so less than 85 is "normal" operating pressure. Everything in the irrigation system should be safe if you set the compressor at about 70 PSI output, even in a closed system, like when the controller doesn't have any zones open. It's designed to handle the pressure it can see from the utility. (cont'd) – fixer1234 Nov 20 '17 at 1:26
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    You don't need to shut off the compressor before the whole job is done, or worry about trapped pressure between steps. There is also no problem with zero water or air pressure in a zone. That's the normal state when a zone isn't running because the nozzles are just holes; a zone doesn't retain pressure when it's off. The reason to blow out the plumbing is that if the residual water freezes in the winter, the ice can't escape through the nozzles and can crack the nozzles or even separate or crack the tubing. – fixer1234 Nov 20 '17 at 1:26
  • Wow, this is so similar to what I have, minus #5. – grokus Oct 23 '18 at 20:54

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