Computer Prog wrote:
I have a small 4-zone system at my house.
I have a Sears 5.5 HP 25 gallon compressor that is rated at 8.6 CFM @ 40
PSI and 6.4 CFM @ 90 PSI. I have 50 feet of 3/8 copper tubing in a coil at
the output of my compressor going to a water filter and a quick release
fitting. I ran 75 feet of ½" rubber air hose (after the 50-ft copper coil)
out to the drain plug below my Wilkins breaker. I filled my compressor,
turned on one zone of my sprinkler and set turned my compressor regulator
to 50 PSI of output. I heard a lot of "gurgling" at the Wilkins breaker
but my sprinkler heads did not pop up. I raised the pressure a bit to 70
PSI but the sprinkler heads still did not pop up.

Hi, I am not an expert at this, but you haven't gotten any other
replies in the last 48 hours so i thought i would share my experiences.
I have a 6 zone system that covers just under a third of an acre (sorry
no measurements handy). I also have a Sears compressor - mine is 25
gal, 3.5 max/1.6 operating HP and a pressure up to 175 PSI. According
to the specs mine is rated at 5.6@40 and 5.1@90 - so yours is pushing a
great deal more air than mine is.
I do essentially the same thing in that I pressure up the tank and run
50ft of rubber air hose to the point where my pressurized irrigation
feeds into the sprinkler valve box. I have a special fitting I built
from parts that connects the air hose to a hose bib on the irrigation
system. I turn on one zone and plug in the air hose quick connect to
let it rip. My compressor has no trouble in raising the heads on my
sprinklers. I don't recall what specific pressure I set it to though.
I do recall starting out sort of gently and then slowly increasing the
PSI until it would lift the sprinkler heads though - i was afraid of
blowing things apart initially.
I guess i don't get the purpose of the 50ft copper tubing - is this a
water trap or other?
It seems based on my experience that you have the horsepower and there
may be something else going wrong.
Good Luck,
Matt