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
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.
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?
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 .
I then choose which zone to blow, and manually open its valve.
I wait until the compressor tank gets up to pressure, and _slowly_ 
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.
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.
 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.
 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
 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
It's not just anyone who gets a Starship Cruiser class named after them.
I have 7 zones the installer told me not to worry about blowing it out and I
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.
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
Be safe not sorry. I live in central Illinois and it gets colder than heck
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
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.
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