Any inexpensive Dew-Point Monitors for air lines?

Don't kill yourself. You can run the air through the RAD and tack a simple separation unit on the outlet as well. Also doesn't hurt to run a roll filter in front of the RAD to keep the crap out of it.

Like this type.

I don't see why the refrigerant sight glasses wouldn't work at least technically. They can certainly handle the pressure and are expecting to see gas or liquid at any point. It may be that they are too sensitive and would only show wet at all times since a refrigerant system should be a lot drier than even a well dried air system.

Cheap and Easy would be a thermometer on the chilled air line and a clear water trap downstream. Dew Point is a function of temperature and unaffected by the pressure.

You can make the dessicant that turns color from calcium chloride (ice melter) plus a little cobalt chloride. In second grade we mixed up some to make humidity indicators for a weather project, along with light-bulb (vacuum) barometers. The throw-away HF in-line air driers are an easy source of cobalt chloride mixed with silica gel.

jsw

Some folks use big drip legs, with brass valve at the bottom, and open the valve daily to blow out the water. I guess you have more water than this?

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Keep glass-bottomed regulator/filter at the end of your line, and push the spring-loaded drain thingy before each shoot. Inline filters are great for spray guns, too. Cheap insurance.

-- Never trouble another for what you can do for yourself. -- Thomas Jefferson

McMaster Carr sells silica gel air dryers that change color (blue -->

pink). They are probably the same as the "Magic Eye" ones that you mention, but the ones with an aluminum bowl are rated for 150 psi and the desiccant can be regenerated by heating.