Designing Kitchens and Bathrooms - Removing Cast Iron Tubs

I am about to remove a standard 58" cast iron tub (ca. 1965 I think) to replace it with a newer water jet tub. My first instinct, since I don't want or need the tub being removed, is to take a sledge hammer to it after I disconnect the drain (tile is going too). Does anyone have any experience doing it this way or want to warn me not to for some reason? It seems a lot easier than trying to get it out in one peice. Any thoughts?

Also, do jet tubs need an intake in addition to the spout or do they just pump water around that is already in the tub? Otherwise, how do they prevent backflow?

-Curious...

Using the sledge hammer to break up the old tub will work just fine. Just dress appropiately. The small chucks of cast are sharp. Long jeans, a heavy shirt or sweatshirt, at least goggles, though a full face shield would be better, a hat,... Just don't get overly carried away with the hammer. You only want to break up the tub, NOT move the walls it is attached to, or crack the sheetrock on the other side.

Also, just because the tub has a porcelien coating doesn't mean it is cast iron. It may be a pressed steel tub (they look the same from the outside). If the sledge hammer dents it without breaking it, stop and remove the tub as a unit. It's pressed steel.

spa tubs recirculate the water that is in the tub. no way for backflow.