Water should come out of the back of a wind unit when it is humid out, usually a drain hole. If water is leaking inside from a window unit, check that the outside drail hole is not clogged or maybe it is not tilted downward enough outside (Usually a very slight tilt down toward the outside to help the water drasin out the back outside). Also, if you have excess water forming, you may need to clean the coil. For central air units water should be drippng outside the home via a pipe or tubing and if the drain tube or pipe is clogged with scum that forms inside the pipe water will back up and overflow in the house near the heater/air conditioning unit. Also, some units have a pump to pump the water out and it may not be working.