[AT] PTO compressors

[Richard Walker]

> Tom, the company that used to handle his system went out of business which
> left a major void in the county he lives in. He may work something out with
> neighbors if he invests in a compressor, don't know.
>    

Reading this thread and never having to face problems like this after 
living a lifetime here in CA, I idly wondered why something as simple 
and cheap as a large (350-450 CFM) leaf blower temporarily plumbed into 
the irrigation system would not work to clear water from the piping, 
since at first thought it seems large air volume but not high pressure 
would be all that's required.  After a little googling out of curiosity, 
I found out I was dead wrong and the evacuating operation is a LOT more 
complex than that:

http://www.irrigationtutorials.com/winter.htm

Scroll down to "The Blow-Out method".

Sounds like with all the potential for damages to a system, your 
neighbor better be well bonded and insured before doing any work for hire!


-  Richard

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The Blow-Out method:

    * This is not a method I recommend for amateurs! It is not a project
      for the average "do-it-yourselfer". Almost all big sprinkler
      systems such as golf courses and parks are winterized using
      compressed air. But one tiny little mistake-- and you will no
      longer own a sprinkler system. You will now be the proud owner of
      a bunch of buried plastic shards! So I recommend leaving this
      method to the professionals. If you try it and one of your
      sprinklers is launched like a bottle rocket, don't come crying to me!

    * In order to blow the water out of the pipes you will need an air
      compressor, and it can't be just any air compressor! It needs to
      be a big, *BIG* air compressor. Probably bigger than that
      compressor you already own. In other words that high pressure, low
      volume compressor you use in the shop is not the right compressor
      to use! (Did I mention this isn't a project for the average
      do-it-yourselfer?) How big you ask? For a really small irrigation
      system (3/4" PVC pipe or 1" poly pipe) you will need at least a 20
      cubic feet per minute air compressor. And that is so small that it
      is not going to do a very good job! Most experts recommend nothing
      smaller than a 50 cubic feet per minute compressor for a home
      sprinkler system. Professionals often use a large gas or diesel
      powered compressor that can discharge over 125 cubic feet per
      minute of air and can blow out a pipe as large as 3" diameter. For
      pipes over 4" they use a 250 cubic feet per minute compressor.
      Note: SCFM means "Standard Cubic Feet per Minute" and for our
      purposes here, it's the same thing as CFM. SCFM is a measure of
      CFM at a specific temperature and altitude.

    * Here's what you should *NEVER* use. Do not use an air tank filled
      with compressed air or gas. Do not attempt to create more air flow
      by filling an air tank, then attempting to blow out the system
      with large bursts of air from the tank. Do not try to connect the
      exhaust pipe of your car (truck, boat, cow) up to the sprinkler
      system. Do not try to use a leaf blower or a vacuum cleaner with
      the flow reversed. Forget about using your electric tire pump
      (most of them have a hard enough time just inflating a tire!).

    * Each sprinkler system is different. I strongly suggest renting an
      air compressor rather than buying one until you have found an air
      volume that works well for you. Many variables effect the proper
      selection including local altitude, temperature, and type of pipe.
      Besides, it's probably a whole lot cheaper to rent one once a year.

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