Blowing out sprinkler lines

I haven't blown out my sprinkler lines of residual water yet. This is the first house I have owned that has sprinklers and I am getting conflicting advice on what I should do. Some people said it really isn't necessary because since I haven't used the sprinklers in over a month there isn't much water in the line. Other people have said it MUST be done. I haven't bought an air compressor yet. Kind of stuck on what to do and what I would actually need to do it (i.e. size of air comp., what fitting I need). TIA for all tips and opinions
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What did the previous owner do, depending on system design you may be fine but wont know till you turn it back on. Hire a pro the this year and learn from him. A small compressor may or may not do the job.
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A properly designed and installed sprinkler system will have drain valves that open when the pressure is removed. If you don't have drain valves in yours where does the water in the system go?
EL
Rennyboy wrote:

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Not all systems have drain valves. The more expensive ones do. If yours doesn't, the system will have to be blown out. In my area, they charge $60 to do an 8 zone system.
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Unless you _know_ that the sprinkler system has automatic drain valves that really do work, you need to blow the lines. While an all-plastic sprinkler system may survive a winter without being blown, it probably won't survive more than one. Especially if you have valves outdoors.
The first year, I didn't blow the lines at all. Survived okay, but it didn't have any valves in it - all manual.
The second year, I installed valves, and rented a compressor to do it.
Since then I've been doing it with a homebrew compressor.
[Originally a Campbell Hausfield 3/4HP tankless compressor unit, I added one of those tire-fill 4 gal tanks and standard air fittings to it.]
As for how to:
In my case, I replaced the hose "standard" (hose bib with faucet and male hose connector) with a "Y" assembly (3/4" copper thruout).
One branch of the Y goes to the sprinkler system. The other branch has a valve and hose male connector for what's normally a ordinary water hose.
When I need to blow the lines, I shut off the water inside the house, remove the hose reel, close the hose valve, and connect the compressor to the Y's male hose connector [1].
I then choose which zone to blow, and manually open its valve.
I wait until the compressor tank gets up to pressure, and _slowly_ [2] crack open the hose valve. Close the valve (slowly) when the line is clear or the tank pressure goes down too low.
Wait for the compressor to build up a head again, switch to whichever zone I want to blow next, and then open the hose valve.
Rinse, Lather and Repeat[3].
Some pros have little gadgets that allow them to "seal" all but one of the heads on a zone, blast, and then switch to another head. I don't bother.
[1] Built an adapter of a standard 1/4" air hose "M" fitting (1/4" MPT on other end), 1/2" MPT to hose female, and a galvanized adapter (1/4" FPT to 1/2" FPT) to attach them together.
[2] My hose valve is a 1/4 rotation ball valve. It's best not to pressurize the irrigation system at _all_. Do it slowly, otherwise, you'll blow the irrigation system's connectors apart. Keep the pressure in the lines below 25PSI - one way to do this is crack the valve only a teensy bit until you start blowing air, then open up a bit more to get the rest of the water out. If it's shaking, you're driving too much air and could blow a connector.
[3] To blow continuously, you need a pretty beefy compressor (but you still need to regulate flow). With my setup, it usually takes 3 recharge/blast cycles to clear each zone. I have 7 zones in service now, some of the zones have as many as 10 heads.
--
Chris Lewis, Una confibula non set est
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I have 7 zones the installer told me not to worry about blowing it out and I did not.
No problems come spring everything worked fine.
I do have a compressor its a commercial unit 80 gal tank so I decided to start blowing mine out, and after not using the system over 3 week period, and blowing it out, using about 90lbs of air pressure, there is allot of water that comes out at the low end of the system.
I don't know if a small compressor would do the job.
Tom
over winter

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Be safe. Blow your lines out. If your temperature gets below 30 in the winter shut you water supply off and blow them out. Also, Be sure you remove the brass backflow valve and cover the ends of each pipe. I use a baggy and rubber bands on mine. If you leave that valve on and the water inside of it freezes and ruptures/cracks the diaphragm you are in for a BIG expense replacing it. Be safe not sorry. I live in central Illinois and it gets colder than heck here.

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I
You must live in an area where the ground does not freeze. Here in Minnesota, not blowing water out of your irrigation system would be foolish. You'd have big problems come spring.

You have a big enough compressor, just ease back on the psi a bit. The safe way is to go high volume, low pressure. Air gets hot when compressed, and irrigation systems are not meant to stand up to much heat. Same with high pressure air. 50 psi or less is fine. Air pressure does not have the same affect on your system as water pressure. A high pressure blast of air could launch your sprinkler heads. So go low pressure, hi volume.

Not a really good idea. You might get away with it, but I'd be wary. There is a reason that the irrigation companies use those large high volume compressors.

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DaveG wrote:

Hi, I am in Alberta. Blowing the system out is must at around October. I use shop compressor I have. Set at around 50 PSI, takes little longer than big commercial compressor but zone by zone it does the job. One reason I bought the compressor. Can't pay 30.00 - 40.00 every season year after year. Tony

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