Unable To Blow
November 6, 2016 2:23 PM   Subscribe

I'm trying to blow out the sprinklers on new sprinkler setup and can't figure out what part I need to connect up to my compressor. Here is a photo.

I can't seem to get any of my copper brass fittings to fit onto the test cock (on the right side). The fitting is 1/8" (the 1/4" air connector is too big). What am I doing wrong?
posted by shew to Home & Garden (3 answers total)
Best bet is to close the valve behind it, remove just the air nipple from your house, and take it to the hardware store and try adapters that're compatible with your compressor.
posted by Sunburnt at 3:38 PM on November 6, 2016 [1 favorite]

Looks like a 3/8" flare fitting (hard to judge scale could be 1/4 or 1/2). You need a 3/8" flare nut, a short length of copper tubing with a flare, a 3/8" compression to 1/4" NPT union (like this but 3/8"-1/4") and a male 1/4" air bayonet connector that matches your compressor (usually Type 'M' in consumer grade equipment).

Sunburnt has a good idea if you aren't sure on sizes. Though if that flare adapter isn't integral to the valve (IE: it threads out) you can just buy an Air Bayonet fitting that matches your coupler and has the same threads as the valve. Way cheaper than transitioning.
posted by Mitheral at 3:56 PM on November 6, 2016 [1 favorite]

After we got a spigot installed at the far end of our yard, we had the same problem.
Mrs. Plinth rigged up this bad boy by ordering parts from McMaster Carr. The 90 degree turn makes it easier to hook up the air hose.
I measured the diameter across the female part and it's 3/8".

Note that the flat head screws embedded into the male fitting are also valves.
What I do is shut off the inside, shut off below the blow-out, hook up the compressor and turn it on, open the spigot, then open the flat-head valve. After it's blown out, I close the blow-out valve and close the valve below.
On ours, there was a little, tiny unobtrusive valve before the pipe goes into the house. So unobtrusive that I didn't know it was there and split the pipe the first winter. The plumber that fixed it installed a much bigger valve. That drains the water in the stretch between the house and the outside and prevents burst pipes.
posted by plinth at 4:27 PM on November 6, 2016 [1 favorite]

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