Bird
Rest in Peace
A 30 lb cylinder has about 4-5 gallons in it
You're a little off on your capacity. LPG is roughly 4 lbs. per gallon, so the little common 20# bottles hold about 5 gallons, the 30# bottles about 7.5 and the 40# bottles 10 gallons.
If anyone doesn't already know it, you'll find a "WC" number, and a "TW" number on the bottles. WC=water capacity (in pounds) and TW=Tare Weight (in pounds). Tare Weight is nothing more than the empty weight of the bottle, and you multiply the water capacity weight by 4.2 to get the weight of the LPG it should hold when full. So TW+(WC*4.2) gives you the proper weight of the full bottle.
Now, that's pretty simple when you're accustomed to it, but does anyone know why they didn't make it even more simple by simply stamping bottle weight or empty weight instead of TW for Tare Weight, and why they didn't just stamp the weight of it's capacity in LPG instead of water capacity?