I have an irrigation system which I need to connect air compressor to. I was told by previous owners that there is an entry somewhere around the area pictured below. I assume it is either in one of the boxes pictured, or under rocks somewhere nearby.

area of interest

Contents of each of the boxes are below.

Questions I am trying to find answers to are:

  1. Where can I connect air compressor to? Is it in one of the boxes, or somewhere nearby? If it is not in one of the boxes, where would I look for it? It seems like it has to be between #2 and #3, or #3 and #4.
  2. Should I do anything to the double check backflow preventer for the winter?
  3. What is #5? It might be unrelated to the irrigation system.

#1 - irrigation system shut-off valve

box number 1

#2 - not sure - double check backflow preventer?

box number 2

#3 - not sure - some sort of pressure control?

box number 3

#4 - zone valve

box number 4

#5 - not sure

box number 5, closed

box number 5, open

  • 1
    #5 looks like an old messed up air coupler, something I would probably toss out and replace.
    – crip659
    Nov 12, 2022 at 2:02
  • Air compressor for what ? Winterizing (blowing out water) before freezing? sorry for the question, I live in AZ and we do not do that.
    – Traveler
    Nov 12, 2022 at 3:08
  • Picture of the pipe that feeds it from inside? There should be a valve and a spigot for draining it before it leaves the house. Get an air hose gun nozzle with big rubber cone on it and just hold it there. amazon.com/Capri-Tools-Rubber-Blow-3-Piece/dp/B074T646QZ
    – Mazura
    Nov 13, 2022 at 0:08

2 Answers 2


Your picture identifications look correct. My system has a hose bib which you then use a air to hose adapter to pressurize before winterizing.

I'd guess that #5 is an air coupling that is used to pressurize the system. I'd expose that connection and see how it is hooked into the irrigation system. Possibly your system has the air coupling permanently attached to the irrigation system. Not sure how you'd clean that out so you aren't blowing crap into the irrigation system if that is indeed the pressurization point.

  • You are right, after digging it up #5 turned out to be connected to the irrigation system. Nov 14, 2022 at 0:42

See if you can open any of those fittings that would help you hook up your air hose to it. Typically there should be one right after that back inline shut off valve as in that first picture. The closer to the shut off, the better.

Large volume of air need to enter the pipes at once. Typically this is done by opening a spigot or any spot that has such opening. You need at least 80 psi of air pressure. Before opening the air, make sure the valve to a zone is open. You do not want to blow such high pressure air to a closed zone with all that pressure nowhere to go.

See picture as to what is meant by an open pipe. You can purchase air fitting that will hook up to a spigot or a set up that is one like it. Either male or female.

Okay, hope this helps.

Take care

Hooking up air connection

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