I live in Murfreesboro TN. There is a business in town called, Boiler Supply Co. they, service, sell, repair boilers. I talked to Dave the owner he gave me a copy of TN State Law. I can build my own boiler if it is smaller than 5 gallons. It does not have to be, inspected, tested, licensed, or anything. I built a 4.9 gallon boiler for my 4"x4" steam engine it ran the engine good.