I bought a new air tank at carlisle for a semi for 35.00 - it has multiple fittings, and a port for a drain, and it is code stamped for the pressure rating. Everyone here is right about the oil drum - code stamped pressure equipment is the only way to go - and the couple of bucks extra prevents explosions that can leave you dead, or even worse. that 150 psi air tank can flip or destroy a vehicle if its of a good size - the pressure packs a lot of energy.