"Cheap" Hydrostatic Testing Chamber As background information, I'm a computer programmer by trade but I want to get into underwater ROVs as a hobby because I need a hobby that doesn't involve sitting in a chair all the time, because Bob Ballard was one of my heros as a child, and because there are a lot of fresh water lakes near my home. I've done a lot of reading about the existing state of RC submarine technology and they seem to come in the wet hull and dry hull varieties. Most people build wet hulls because they are simpler. Despite the added complexity, I want to build a dry hull because it has higher buoyancy and would allow me to carry extra batteries, servos, electronics etc. I'm in the process of researching what materials to use for the hull(PVC, steel, aluminum, etc) but to minimize the weight of the hull I need to be able to pressure test the design so that I don't risk losing my submersible/work at the bottom of a lake. The deepest lake within driving distance of my home is approximately 400ft deep so at .432 pounds per foot of fresh water depth, with a 50% safety factor, I want to be able to pressure test the hull to approximately 250psi. 400ft is the theoretical maximum that I'd ever want to go. At my skill level, that would be like landing on the moon. I may never get there but I enjoy the challenge of designing for it. Typically, my sub would operate at a depth of 20-100ft, because that's the depth of the lakes which are closest to me. So, what I want is a cylindrical pressure vessel, that I can open from one end, which has an internal diameter of approximately 12" and a length of approximately 8' which can safely withstand an internal hydrostatic pressure of 250psi. Those internal dimensions should comfortably fit any ROV that I would ever attempt to build. I would then use a hand operated hydrostatic pump(typically used to hydrostatically test compressed air tanks) to put the desired pressure into the chamber. This would give me the confidence that my hull isn't going to buckle but, more importantly, that none of my shaft/wire seals, which penetrate the hull, leak. Does anyone have any practical suggestions on how to build such a device?