Size compressor to blowout irrigation pipes

Reply

  #1  
Old 07-05-17, 06:57 AM
Q
Member
Thread Starter
Join Date: Jun 2014
Location: Canada
Posts: 1,778
Received 1 Vote on 1 Post
Size compressor to blowout irrigation pipes

My irrigation system runs off a pressure tank at 30-50 psi with polypropylene pipe.
The longest run is about 200ft and it supplies around 10GPM.
What size compressor should I get to blow it out? 10cfm or less should be fine but how many gallons is required at a minimum?
 
  #2  
Old 07-06-17, 02:25 AM
Marq1's Avatar
Member
Join Date: Sep 2016
Location: USA MI
Posts: 7,142
Received 462 Votes on 430 Posts
I use my shop 60 gallon compressor and it does a great job, I've seen folks do it with a 30 gallon but it takes some time.

Anything smaller and your going to run out of air before you can get the water out.
 
  #3  
Old 07-06-17, 06:04 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 13,946
Received 298 Votes on 258 Posts
I think my compressor is a 12 gallon and as Marq1 says, it just takes more time to get the water out. My runs are not very long though. Longest one is maybe 80' 3/4 pipe and 4 heads.
 
  #4  
Old 07-10-17, 06:33 PM
Q
Member
Thread Starter
Join Date: Jun 2014
Location: Canada
Posts: 1,778
Received 1 Vote on 1 Post
what connector do I fit to the 3/4 polypipe so that an air compressor can connect to it?
 
  #5  
Old 07-10-17, 07:38 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 13,946
Received 298 Votes on 258 Posts
How you connect will depend on your system. When planning my system I added a Tee fitting with a 3/4" threaded female adapter. Then I bought a brass 3/4" cap, drilled and taped a hole, and installed a air hose fitting like you would install on an air tool. That connects directly to my air hose.
 
  #6  
Old 07-10-17, 07:47 PM
Q
Member
Thread Starter
Join Date: Jun 2014
Location: Canada
Posts: 1,778
Received 1 Vote on 1 Post
What did you have to drill a hole in? Isn't there a fitting that can go straight onto the water system?
I have some 3/4 barb tees with a 3/4 male thread...
 
  #7  
Old 07-10-17, 10:26 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 18,157
Received 69 Votes on 61 Posts
Geez guys I blow mine out with a 3 gallon compressor...
 
  #8  
Old 07-11-17, 06:04 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 13,946
Received 298 Votes on 258 Posts
What did you have to drill a hole in? Isn't there a fitting that can go straight onto the water system?
As far as I know, there is no fitting to connect an air line of a compressor, to a water line for irrigation. So, You have to make one using whatever fittings work for you.

I have some 3/4 barb tees with a 3/4 male thread
So get a 3/4" female cap. drill a hole and install an air hose fitting that will connect to your compressor air chuck.
 
  #9  
Old 07-12-17, 03:05 AM
Marq1's Avatar
Member
Join Date: Sep 2016
Location: USA MI
Posts: 7,142
Received 462 Votes on 430 Posts
Or connect to your back flow preventer if you have one.
 
  #10  
Old 07-12-17, 07:27 PM
Q
Member
Thread Starter
Join Date: Jun 2014
Location: Canada
Posts: 1,778
Received 1 Vote on 1 Post
Ok, the part I'm confused on is the cap.
A 3/4 cap is a threaded cap that you drill a hole in.
But there's no threads on the other side, so how do you connect the air compressor to the cap?
Secondly, assume air pressure works similar to the pressure built up in the water system. If you drill a small hole in the cap, aren't you reducing the amount of air that can flow through the system to the size of the small hole?
 
  #11  
Old 07-12-17, 07:44 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 13,946
Received 298 Votes on 258 Posts
You missed the part in my post #5 that said I taped the hole to fit the air line fitting.

Buy one of these: Everbilt Lead-Free Brass Pipe Cap 3/4 in. FIP-801989 - The Home Depot

Buy one of these: Husky 1/4 in. MNPT x 1/4 in. I/M Steel Plug-12224HOM - The Home Depot

Drill and tap a hole to fit the air fitting. The 1/4" hole is more then enough for air to flow and push out the water. Just think how fast the air comes out an air hose when you disconnect it from a compressor.

You could also try to find a 3/4" to 3/4" coupling and then reduce it down to the air fitting, but IIRC it was cheaper for me just to drill a hole and tap it.
 
  #12  
Old 07-13-17, 02:22 AM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
Rather than having to drill and tap a cap why not use a 1/4 by 3/4 inch bell reducer?

Or, better still, connect a garden hose connector to the largest port on the air tank (use a ball valve in between) and then a short length of garden hose to the sprinkler system. It is VOLUME, not pressure, that you need to blow out the water.
 
  #13  
Old 07-14-17, 07:41 AM
Q
Member
Thread Starter
Join Date: Jun 2014
Location: Canada
Posts: 1,778
Received 1 Vote on 1 Post
garden hose is usually 1/2" connectors?
If so, could I just put a faucet onto the 3/4 polypipe and then connect the air compressor to the faucet and open it?
 
  #14  
Old 07-14-17, 07:44 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 13,946
Received 298 Votes on 258 Posts
Garden hose is a special size. They do make adapters from garden hose to plumbing thread.
 
  #15  
Old 07-19-17, 07:03 AM
Q
Member
Thread Starter
Join Date: Jun 2014
Location: Canada
Posts: 1,778
Received 1 Vote on 1 Post
The part I am confused on is how to get the air connector into a plumbing thread?
The suggestion was to drill a hole in a plumbing cap I think, but then I'm not sure how you would attach an air compressor to that, they're all different sizes.
 
  #16  
Old 07-19-17, 08:15 AM
A
Member
Join Date: Jan 2013
Location: U.S.A.
Posts: 2,103
Received 72 Votes on 65 Posts
Not sure if I am understanding your question or not, but taking a stab at it. Are you asking how to connect the coupler on the end of the air compressor hose to NPT? You can either remove the coupler from the end of your air hose, leaving you with a standard NPT to connect with, or you can buy a nipple at your local auto parts store, hardware, or big box, which you can thread into your system and then connect your air hose to.
 
  #17  
Old 07-19-17, 06:40 PM
Q
Member
Thread Starter
Join Date: Jun 2014
Location: Canada
Posts: 1,778
Received 1 Vote on 1 Post
I thought water NPT and air NPT were different sizes? ie you can't get compatible?
If you can then why drill holes in caps, etc. Why not just get a 1/2" threaded nipple connect to a 1/2" female on the water pipe and a 1/2" female on the air hose?
 
  #18  
Old 07-19-17, 08:18 PM
B
Member
Join Date: Jun 2014
Posts: 14
Received 0 Votes on 0 Posts
Name:  IMG_2003.jpg
Views: 1077
Size:  19.6 KB


Pretty sure he means a cap like this (probably not pvc) drill hole in end of cap tap it and thread the air chuck/barb in
 
  #19  
Old 07-20-17, 06:01 AM
A
Member
Join Date: Jan 2013
Location: U.S.A.
Posts: 2,103
Received 72 Votes on 65 Posts
"I thought water NPT and air NPT were different sizes? ie you can't get compatible?"

There are of course different thicknesses of pipe and fittings, with varying pressure ratings, depending on the application, but NPT threads are NPT threads, whether used in water or air or whatever. So, for what you are doing qwerty, it's simply a matter of having the right fitting(s) to adapt your air compressor hose to your water line. The only hiccup would be, and this may be where you thought there was a difference, is that garden hoses and spigots use a unique 3/4" garden hose thread.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: