That's the name. I am wondering what the best way to cut the top on one is, will you lose structural integrity ?
reciprocating saw, drill an access hole near one corner first. You don't have to cut all the way to the sides if you don't want the whole top of the tank open. I don't think it would cause any problems, but if you're concerned, just don't cut the metal braces going across the top of the tank.
There's a few companies that make adapters for the valves to connect to a garden hose or smaller PVC pipe.