The cost of plumbing remodeling or renovation might be high. Plumbers, like electricians, attend a trade school, work as apprentices for years, and ...
To create holes, use a brace and bit to drill through the flooring, and then a keyhole saw to widen the entrance. Make sure that the holes are not exactly above a floor joist when you drill them. In fact, the joists & studying must be spared as much as possible while installing the water heater equipment.