Hi I have a few questions.

1) The pic below is of the outdoor water pipe in my backyard. Inside the basement is a shutoff valve for the outdoor water supply. The red tap is another shutoff for the outdoor water supply. The blue tap is for the garden hose. The hose attachment thread for the garden hose is a bit obscured in the pic. The tubing that goes past the garden hose valve is for the sprinkler supply and it enters the ground.

My question is, as long as of course the shutoff valve in the basement is off and the red tap is closed, can I hookup a compressor to blow out the water from the sprinkler lines? The reason I ask is that when I read the product description for blowout compressor adaptors, it states; "Do not connect to the hose faucet attached to your house". So not sure why?. How would water feed back into the home?

Sprinkler water supply tied into the garden water supply

2) During the winter, when the shutoff valve in the basement is off and the red tap is off, is it safe to say, I should not be worried about water freezing in the pipe for the portion of length from the red tap to the bricks?

3) What is this green contraption? it located on the front lawn close to the sidewalk.

enter image description here



  • You are wanting to blow out the water in your sprinkler line. Why would you need to attach the compress to the faucet. You would attach the compressor to the line going to the sprinkler. – Programmer66 Apr 30 '20 at 23:32
  • The line coming out the wall is for both sprinkler system and the garden hose. The only way to attach the compressor line it seems is to the garden hose faucet. I recently moved into this house, so the previous owner hired someone to open up the sprinkler, inspect, adjust the sprinkler heads and then winterize. I am trying to determine whether the sprinkler service company used the garden hose valve to hook a compressor up to it. – GusG May 1 '20 at 0:42
  • the red tap should have a vacuum breaker on it – jsotola May 1 '20 at 2:05
  • the other end of the pipe with the green popup is at a downpipe from roof gutters ... you should see a bunch of water pour out of the green popup every time it rains – jsotola May 1 '20 at 2:08
  • Jsotola, you are absolutely right. That is what it is. I checked the downspout and it is connected to another pipe going underground, I follow the strip of yellow grass and it leads right to it. I just move into this home recently – GusG May 1 '20 at 18:58

Any municipality I know has a requirement for an anti-siphon valve in the supply for a sprinkler system , many require expensive spring loaded valves. Considering that the many users of municipal water may be at various elevations ,it seems likely water could siphon back into the system . Especially if there is a failure of pressure in the municipal system. Any water in the system can freeze ,even with open drains at the low points. I thought the main advantage of a sprinkler system is that it comes through a separate meter and is billed at a lower rate than "house" water. My sprinkler water is half of less than the price of the house water .

  • Aside: Municipalities have differing rules for irrigation. Some may offer separate meters and rates, others offer nothing. Where I lurk the water bill includes sewage fees. The arrangement here is that you can request a change in billing to account for watering. They will then use your winter water consumption to figure the summer sewage charge on the assumption that the increased volume of water is not being returned to them. There is no discount on the water since it is the same potable fluid regardless of what we choose to do with it. – HABO Feb 4 at 3:56

If the pressure generated by the compressor is high enough it could force non-potable water back into your system but not if you have both of the shutoff valves you mentioned in securely off positions.
If your climate is like much of North America (cold in winter) you should drain your sprinkler system and either shut off outside faucets or install freezeless faucets. Understand that freezeless faucets only work if hoses are disconnected in cold weather.
Lastly, I have no idea what that green thingie is in your front yard - maybe someone else does. It looks like a vent or sprinkler head of some type.

  • That is why I don't get, even if you have just one of the two shut-off valves turned off, how can non-potable water go back into the supply. The water pressure coming out through the pipe would prevent any backwash. Does what I explained make sense? Could I also put insulation wrap around those pipes. I moved into this home last fall, so the previous owner hired someone to winterize the sprinkler system. This is how they left it, so I assume I am just been overly cautions. – GusG May 1 '20 at 0:44
  • 1
    You could wrap the exposed pipes with insulation or heat tape but it's no guarantee that it won't freeze. It depends on how cold it gets. But what's the point? You still have to winterize the sprinkler system. Being buried doesn't prevent it from freezing. So to winterize I would turn off the water from the house, blow out the sprinklers, disconnect the hose from the spigot and you're good to go. – HoneyDo May 1 '20 at 4:37
  • Thanks HoneyDo for the clarificiation. – GusG May 2 '20 at 1:16

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