Flushing air lines with water?

1967marti · Aug 22, 2014

Probably a stupid question, but it popped into my head as I was installing copper airlines into my shop yesterday. I was taught to clean off any flux after I was finished sweating copper water pipes and after you finish you let the hot or cold water flow for a bit to wash out the (water based) flux from the inside of the pipe.

My question is: if you are making airlines with copper, should you flush them with water to clean out the flux that wicked to the inside of the pipe? I'm wondering if the corrosive effects of the flux with do any damage?

Pete F · Aug 22, 2014

Were you soft soldering or silver brazing (the latter the plumbers here insist on calling "welding")? Do you know what type of flux it was? Some basic fluxes were acidic in the G.O.D.s so it would probably pay to flush them out. If you can properly drain the lines afterwards (and you should be able to if you've designed it properly) it would be safest to flush them out.

Lakeside53 · Aug 23, 2014

yep - just connect the garden hose and flush away. Can't hurt and your air won't stink of flux for weeks if you do.

1967marti · Aug 23, 2014

I used the silver bearing solder used on ac systems. The flux was a water based type. I'll go ahead and flush out the lines as soon as i'm finished with the last leg.
Thanks for the advice!

- matt

Mark Rand · Aug 23, 2014

Useful tip for next time:- Sil-Fos alloys are used by A/C installers because they don't need flux for copper-copper joints.

Don't use them on a locomotive boiler though, sulfer from the coal reacts with the phosphorus in the alloy and rots it... Don't use it on ferrous metals either.

1967marti · Aug 23, 2014

Thanks Mark, I will go that route if I end up moving locations and need to re-plumb. I used some Bridgit-Water-Soluble-Flux as that was recommended by the guy behind the counter at the shop I got the solder from (stay-brite brand). I figured all flux for copper soldering would do the same, but this stuff tended to not burn as much since I needed to get the pipes a little hotter for the fancy solder.

adama · Aug 23, 2014

Above all think what the flux residues could cause as issues in pneumatic systems. Some solinoid valves, timers and such don't need much in the way of contamination to hang up badly.

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Flushing air lines with water?

1967marti

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Lakeside53

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Mark Rand

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adama

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