said by UHF:said by TheMG:Actually the "20lb" is the capacity of the tank, in other words the NET weight of the propane when full.
Empty tank will weight less than 20lb. Typically around 16-18lb.
So a full tank will be about 36-38lb (GROSS weight).
Yes. Every 20# tank I've run across has had a tare weight of 18lbs. Except the one time a guy brought a fiberglass tank to have filled, but I believe that all of those have now been recalled.
One thing I've come across is the exchange services (Blue Rhino/Amerigas) have downsized the amount of propane they put in the exchange cylinders that you find outside of your typical home center or supermarket from the full 17.5 lbs to 15 lbs. A 20 lb cylinder is designed to hold 17.5 lbs as they are intended to be filled to 80 percent of their capacity. Also places that do flat rate fills also shortchange you on propane.
Best bet is to find a dealer that fills your tank and charges by the gallon. I have two cylinders and I bought them empty (one at Home Depot and one at Lowe's), had them purged and filled. I have the same cylinders that I have since I bought my first gas grill. I have them filled at BJ's since I get member pricing and they charge by the gallon so I don't get charged full price for a partial fill.