I have a small 4-zone system at my house. My property is about 100 feet
deep and 50 feet wide so the sprinkler system does not really cover much
land. The system has a Wilkins Model 420 Pressure Vacuum Breaker right
where the main water line comes out of the house before it goes to the four
zone valves. There is a drain plug in the main water line outside the
house that sits right below the Wilkins breaker. This drain plug is where
the pressure tap is connected to blow out the system.
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. I had a similar problem
last year but after a while of experimenting I got the sprinkler heads to
pop at 50 PSI and the "gurgling" went away. I am not sure how I got it to
work last year but I cannot get it to work again this year.
Does anyone have any ideas what the problem might be? Is it possible that
my compressor is not flowing enough CFM? Would it help if I pulled my
compressor out of garage and put it near the sprinkler drain plug and used
a much shorter rubber airline to hook up my pressure tap?
Not sure, but I know in general the problem is that your pressure can
be high enough to damage system, while cfm is too low. I'm impressed
that you got it to work last year, as it may with a small system, but
usually wiser to bring in a pro. Irrigation co charged me $60 last
year, seemed reasonable. Got new seed in this year, so I'm still using
125 feet of small diameter tubing will not allow enough air to move through
the system. You will need much larger diameter, or preferably shorter
length. Moving the compressor close to the sprinkler piping would certainly
You're moving too little air. 50 PSI is right, but you need probably
double or triple the volume you're getting at the pressure tap.
Is there a way you can blow it out after the breaker? I also have a
vacuum breaker and I had a similiar problem. Sometimes if I lowered the
air output a little , the breaker would close, then I would gradually
increase the PSI output again.
What I eventually did is put a drain valve after the breaker, with a
seperate shut-off as to not backfeed into the breaker.
What you suspect is the problem is indeed the
problem. You need a lot of volume of air and 25
gallon 5 hp (it isn't really 5 hp) won't do it.
People who blow out irrigation lines here all use
the large gasoline powered pull behind a vehicle
type of compressor.
I think that the issue is with the vacuum breaker. You're losing
pressure there and that is why the heads don't pop up. If you could
bypass the breaker, I think you would be fine. Though, I am not sure
how you can do that without seeing the setup. Is there a shutoff valve
between the breaker and the drain plug? Also, do you know if you have
an automatic drain at the end of each zone? I used to use a 12 gallon
compressor years back on a similar sized sprinkler system at my old
house and it was always sufficient to blow out the lines. Granted, I
had to let the tank fill 1/2 dozen times per zone, but it did the job.
It wouldn't work with the system at my new house due to more zones and
longer lines. Now I'm using a 35 gallon tank. FWIW, I add some
windshield washer fluid to each zone to mix with any remaining water in
the lines when I'm through for added protection. I figure that's good
to -20F. With a compressor, the key is tank size. Bigger is better
when it comes to the size of the air tank. My 2 cents on your
compressor setup: Always use the biggest diameter hose you can and
keep the hose short. The longer the hose, the more pressure loss at
the end of the line. I think that your 25 gallon tank can do the job.
I have a similar compressor and have also seen problems like this
sometimes when blowing out my system. And I've also seen problems
where water mysteriously sprays out of the backflow preventer during
Spring start up.
I'm not an expert on what's inside the backflow preventers, but
essentially it relies on a moving plastic object being pushed by water
to close a passage. I think the problem is that air has a lot less
mass, and the widget may not move as easy with air as it would getting
hit with water. So, I think it must get stuck mid-way, with the air
continuing to go around it. This is probably less of an issue with a
compressor that can deliver more CFM. The ones we have are marginal,
though they will do the job.
I'd try the following:
1 - Go back to running water through it again. This should get the
valve operating properly again. Then you can try air again.
2 - Rap the backflow valve with a hammer to try to free it up without
air on it, then apply air and rap again if still misbehaving.
3 - Take the top cover off the backflow valve. On mine, the thing
comes apart easily with just 3 screws and you can pull out part of the
mechanism. Every time I've done that and put it back together, it's
gone back to behaving again.
Also, the total size of the system is usually not a factor for a home
system. They are set up on zones. You only need to have the
capacity to do one zone at a time. Whether there are 3 zones or 12
doesn't matter. What does matter primarily is the nozzle size and how
many heads per zone.
I blow my 9 zone system with a piddly 3/4HP CH compressor with a
3 gal tank without any trouble whatsoever.
Yes, it can't blow each of the lines continuously, but that's
not the issue here - the air tank will recharge, it just takes
a bit of patience.
Remember: there's water in the lines. If you stick 30PSI or
more of air pressure behind the water, you can damn betcha that
water is going to blow the popups up at least until the first
one in the series blows air.
[In my case, the air flow from the _tank_ is enough to have all
of the popups in a 13 popup string blow air. The popups that are
closer to the air tank fall after blowing air for a while, but the
later ones will still pop.]
If that's not working, you have either a massive air leak somewhere
(which you should hear), or the valve/vacuum breaker/whatever aren't
working the way you think they are, and the air isn't going anywhere.
Yes, 150' of airline seems kinda much, but, that should still
be far more than enough to get more than a faint gurgle.
I think something's stuck somewhere in the OP's situation.
Perhaps the zone valves are being stubborn. I have some where
the manual lever doesn't work.
My system has the water supply "fork" to the underground sprinklers
and a hose bib just beyond the feed shutoff in the house. I turn
off the shutoff, connect the air compressor to the hose bib, open
the hosebib valve, and in turn manually switch each of the zone valves.
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
The lower right side of the picture is the water main from the
house. The left side is the water going to the electronic valves.
I was connected my air line to the removable drain cap seen at
the bottom of the PVC on the right side of the picture. This cap
is before the breaker. I also tried to connect my air line to the
small test port on the upper right side of the picture right below
the Wilson breaker. I didn't try to connect air to the small test
port after the breaker on the left side of the picture because I
was worried that air might flow back towards the valve in the wrong
direction and possibly damage it.
I do not have auto drain valves and there are no other ports I can
connect to. I definitely got the heads to pop last year using the
drain plug but I am not sure what I did. I may have disconnected the
50-ft copper coil that sits on my compressor output. I am going to
try to move the compressor right near the sprinkler valve and run a
short line from the compressor to the sprinkler.
Moving the compressor should help. If you really want to see the
heads "pop", run the water first so the compressor can develop some
pressure in the system. If the water is already gone, maybe your
compressor is inadequate to develope enough volume with high
leakage at the heads.
I put my blowout port after the breaker valve and I have yet to damage
the breaker valve in 6 years by blowing out the lines. Keep your hose
from the compressor to the blowout port as short as possible and blow
out one zone at a time. The longer the hose from the compressor, the
more pressure that is lost at the end of the hose. I agree with a
number of the other posters that have stated that adding a little water
to the lines and then hooking up the compressor will get the heads up
assuming you have no leaks in your system. Once there is little to no
water in the lines, then air alone from your compressor will likely not
raise the heads. If that's the case, then you're done anyway. I've
been winterizing my sprinkler system and a few of my neighbors now for
the past 15 years and all of our systems have survived the winters.
I've gone from a 12 gallon tank to a 35 gallon tank and both have
worked fine. So should your compressor.
I moved the compressor very close to breaker and ran a short hose to the
pressure port. This allowed me to blow out my sprinklers properly. The
breaker stops "gurgling" after I give it enough airflow to "open it", at
which point the air goes to the heads and they pop up. That point seems to
be an indicated 65-70 PSI on my compressor output gauge. Once the heads
pop I can immediately reduce the air pressure and the breaker will remain
open with the heads remaining up. I reduced it to an indicated 50 PSI
after the heads popped up. The heads will remain up even if I dial the
pressure down to an indicated 25 PSI.
My compressor was not able to keep up with the airflow at 50 PSI so the
pressure dropped slowly as I blew out the lines. I had to cut the airflow
to allow the compressor to catch up a handful of times.
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