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Blowing out sprinkler system

Posted by spencer_electrician (My Page) on
Mon, Oct 9, 06 at 0:18

I installed a system this fall and a neighboor did as well. I was asking about blowing the system out and he said a store bought air compressor will not do the trick. Said the comapnies that come out to do it have a truck mounted massive unit. Anyone know if that is the case? Or is there a particular size one from Sears or anything that would do the trick? I hear you should go to each zone and open up a head and just shoot the air nozzle through the inlet. Then open all the valves and master drain valve for the winter.

Follow-Up Postings:

RE: Blowing out sprinkler system

Hello Spence,

I have experience with golf courses in the cold part of my state. The systems are very large and require a large
volume of air to evacuate the system. These systems
do require onsite gas driven compressors. Your lawn however
does not. A simple 5 gal compressor will do the trick but
depending on the size on you system it may take a few recharges of the air compressor. Please remember that pressure is your enemy when blowing out a irrigation system.
Keep the pressure under 70psi (more if you have large elevation changes) otherwise pipe damage can occur.

RE: Blowing out sprinkler system

I have used a residental 19gal air comp. to blow out my system for years now with no issues. I keep the pressure below 50lbs so as not to damage the heads; don't run the heads dry too long or you will find out the following spring that some will need replacing (the water keeps them lubricated). My longer runs take 3 to 4 refills of the tank.

Neighbors hire this all out to a local guy with a tow behind industrial grade unit, but he charges $80-100 per house depending on number of zones (this is standard price in town)

Good luck!

RE: Blowing out sprinkler system

Hmm so the 19 gallon works but I wonder about the 5 gallon divet mentioned. I may be able to borrow a 5 gallon but dn't know if it will do the trick. My system has a 1 inch poly main line that is about 170 feet long. The zones use 3/4" poly and I did put in an automatic drain at the lowest head of each one. So maybe the drains will handle the majority and a small compressor could get the water out that remains in highspots of the pipe. I also put between the main solenoid valve and the master shutoff a hose bib that can be opened to drain the bulk of the main line.

RE: Blowing out sprinkler system

I've used a 12 gallon compressor ($200) for 10+ years without any problem. I do each zone twice, but my longest line is no more than 180' (1" diameter). I don't have a lot of confidence in automatic drains unless the lines are on perfect slopes with perfect drainage at the end. Any peaks and valleys in the lines will prevent the water from draining correctly. At $80 to $100 a shot, I'd consider buying a compressor. But, the irrigation system hookup and blowout process could be a bit intimidating.

RE: Blowing out sprinkler system

I started blowing out my orbitz sprinkler system and got the first two valves to blow out water, but on the second valve I left it blow out longer because water was still coming out and the compressor started up again. Then when I closed the valve the air started coming out thru the flow valve and I can't seem to get it to stop so I can finish the job. Any help or suggestions would be appreciated greatly.

RE: Blowing out sprinkler system

  • Posted by mikie z9 St.Pete.FL (My Page) on
    Sat, Oct 20, 07 at 16:57

Here's some basics.

Here is a link that might be useful: sprinkler warehouse .. winter blow

RE: Blowing out sprinkler system

The size (ie gals) does not matter. You need enough air flow or CFM to do the job. The big units have over 100 cfm. Some recommend at least 40 cfm. I rented a 15-20 cfm unit since no body rented a 40, and it did the job just fine. My system is 3/4 poly, with no sprinkler heads - it is just a burried system to provide water at remote locations. I collected the water at the outlet of the system, and all water was out in a few minutes.

Most home compressures only have about 5 cfm.

It might be of interest to know how to connect the unit. I took off the standard compressure connector (screws to the hose) and the remaining piece fit just perfectly in 1/2 inch hose, which I connect to the system.

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