Best Method for Propane Level guesstimates?

I do carry a scale ==> http://www.amazon.com/Grill-Gauge-GG-1100-Original/dp/B0012GTU3O

I use it mostly at home for the three twenty pounders I keep. My neighborhood filling station charges me $20 for a 20 pounder no matter how empty the tank is. They've charged the same thing for three years - go figure. When camping, I mostly don't worry about it cuz one 20 pounder lasts a looooong time and propane is so easy to find. I do carry a 1 gallon tank for BBQing that I could easily hook up as main if I needed to ==> http://www.amazon.com/Worthington-281149-1-Gallon-Cylinder-Prevention/dp/B000SKX63U

fred

I have two tanks mounted on the tongue with an auto switch.  Makes it real easy.  I can tell at a glance when a tank is empty, but I have plenty of time to get it filled.  It's not a lot of weight anyway, but since both tanks are almost never full, and if they are, they don't stay that way long.  So they don't weigh as much as you might think.

TT

Originally posted by P and D Podders Just how does the warm water method work? I have just returned from a trip to Colorado and after using the heat for 4 nights and cooking we only used 2 gallons. A 20LB tank holds about 5.5 gallons.

It is really quite simple. warm water heats the tank. The liquid is a better conductor of heat than the vapors. Where there is liquid propane, the metal of the tank cools rapidly. You can easily feel that since the part above the liquid level will stay warm enough to let you feel the temperature difference.

You should realize that while you may think a 20 lb tank should hold about 5.5 gallons, the actual capacity is 4.7 gallons. The overfill prevention device will cut off the filling at that point. If the bleeder valve is used, this is also the point where liquid will start to come out of the bleeder valve, indicating full.

This site has some interesting information about tanks and filling:
http://www.elivermore.com/propane.htm

I can already tell you what your review will probably be like.
The gauge on the tank is only a relative indicator of the propane level. When it reads what one would expect to be "empty", it really means that the level is "low." There will still be a gallon or so remaining when the gauge its the red. I though it was a fault, but after talking to the manufacturer, it was explained that this was the case. I don't rely on the gauge except as a relative indicator.

Has anyone asked fwunder his method for checking the propane level? I'm sure there is a PERFECT use of frozen peas.