A word of caution---Every year, people are killed by exploding home made air pressure tanks. It ranges from the guys who make air compressors using old lawn mower engines and cold water pressure tanks to those who make home brewed pressure sandblasters using 45 gallon drums. If you are going to make any kind of pressurized container, try and use a tank that was originally designed to hold a high pressure gas. I am not advising this, but many people who build their own pressure sandblasters use an empty 100 pound propane tank.