I've been reading this thread for a while and I had to join up and comment. The 119 gal limit comes from the Feds! I am a safety director in the trucking industry industry. My first trucking job was for a fuel hauler & I have close to 20 years in the Tank Transport Industry.
Most states hae adopted the Federal Haz Mat regulations [CFR40 172.102] 'in toto' meaning the entire scope of the regulations.
119 gal is the threshold of a BULK package. Bulk packages [tankers & IBC's] are designed and constructed to DOT 'specifications'. That means the materials, construction, venting, safety devices, etc. MUST meet specifications. So does a 55 gal drum but it is not a BULK package, look at the bottom and you will see the specification markings. for example the opentop metal drum used in Haz Waste cleanups is a DOT 17H. The packaging for Haz Mats is designed acording to POP [performance oriented packaging] and will have UN of DOT markings.
It is usually legal to transport up to 1000 LBS of Haz Mat without warning placards on the outside of the vehicle UNLESS you get over the 119 gal. Gasoline is around 6.3 LBS/gal so 119 gal is under the 1000 pounds.
So that's where the arbitrary 119 gal limit comes from.
Transporting ANY amount of Haz Mat, in commerce, requires a CDL w/ Haz Mat endorsement unless it falls under 'Materials of Trade' like the oxy-acetlene torch on a repairman's truck, etc is exempt. So would an individual hauling under 119 gal of gas for his own use.
Remember to ground the drums while you pump them out! Transfer hoses have a bonding wire that contacts the metal end fittings so the delivery hose is always has a ground path to control static. Anyone pumping gas needs a wire from the source to the receiving container. Also keep your discharge hose as far inside the receiving container as possible so it gets covered quickly by the transfering liquid as the splash from the product falling into the container can generate static. Gasoline tankers are 'bottom-loaded' to control static and vapor vented back to the source as fire protection.