We discovered before we left that one tank we were using was almost empty & the one we thought was "full" was completely empty. I had a inline gauge (old style fittings) but it really was not useful. I recall seeing stick on magnetic gauges... not sure if they work. I'm not comfortable with the blind "switch over when it runs out" plan.

Here is a better option...

Or buy propane tank with actual gauges built in like fork lift style tanks do... They are still out there...

W-H-A-T ?? Does that have windows in it? Are you pulling my leg? I don't want to be the butt of one of your jokes...

No joke... http://www.google.com/search?q=clear+propane+bottles&rls=com.microsoft:en-us&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1&rlz=1I7ADFA_en#q=clear+propane+bottles&hl=en&rls=com.microsoft:en-us&rlz=1I7ADFA_en&prmd=ivns&source=univ&tbm=shop&tbo=u&sa=X&ei=4ZXqTY34MYGasAOwq8n5DQ&ved=0CE4QrQQ&bav=on.2,or.r_gc.r_pw.&fp=830c3e2a07ee9aae&biw=1659&bih=882 There you go a Google Shopping page full of them...

That's really neat... learn something new every day! However, the largest offered is a 20#.

The stick on type of gauges do work, but they work by temperature since the boiling LPG is going to be colder than the rest of the tank. All you would need to do is feel the tank with the back of your fingers to feel where the cold line is when you are using propane. That is your level.

Thanks, I've never tried it!