I'm not sure a 20 or 30 quart pot is the ideal solution for boiling water, and the suggestion of troop cooking does not sound very boy scouty to me.
I have serious safety concerns about scouts lifting 30 quarts (7.5 gallons) of boiling water. Even if the pot is not going to be moved, outdoor stoves are not as stable as we would like. Can you imagine the damage of spilling 7 gallons of boiling water? It's a scout outing, not repelling Viking invaders.
Bringing 30 quarts to a rolling boil takes a long time and a lot of heat. To boil 1 gallon of water in 1 hour you need 1,178.6 BTUs; accordingly, to bring a 30 quart pot (7.5 gallons) to boiling in one hour you need 8,839.5 BTUs at 100% efficiency (which never happens). At 100% efficiency a 50,000 BTU/hr. burner will deliver 8,839.5 BTUS in 0.176 hr. (about 10 minutes). But 100% efficiency never happens, and typical heat loss on an outdoor stove is appx. 50%. Under ideal conditions it will take a 50,000 BTU/hr burner about 20 to 30 minutes at full blast to bring a 30 quart pot to a boil. That's a big stove and a lot of propane. Sure you can use bigger BTU/hr. burners, but you're still going through a lot of fuel and probably sacrificing patrol method.
By comparison, to bring 4 quarts (1 gallon) to a boil on a more practical patrol-sized burner that typically operates at 8,000 BTU/hr. takes about 10 minutes. That same gallon on a 50,000 BTU/hr. burner will boil in about 3 minutes.
Of course you actually practice patrol method cooking, and each patrol has it's own stove. Given the limitations of patrol stoves, I suggest that it is lot more practical (and safer) to boil water 4 to 6 quarts at a time.