Whirlpools are characterised by having jets assisting the bath about half way up in conjunction with a suction point (similar to be able to colander) with the bottom four corners. This type of system produces hydro-massage by sucking water from the bath and pumping it right out of the jets quietly under blood pressure. To increase the pressure for this jets most whirlpools possess a control on the top of the bath which allows air become sucked throughout the jet of water. For the cons on an u...