Yeah, looks cool, doesn't it?
It's a bit harder than it looks tho. You need to weld it very strong, completely sealed. And you need a pump that can handle a lot of pressure. Best is a farm machine hydraulic oil pump, as they are used to work on high pressures and oil compresses less then water.
Oh, and this is dangerous, if the welds don't hold you'll have a homemade clusterbomb.