My guess would be is that the inside of your hot water tank has begin to rust, which means that it is only a matter of time before it rusts all of the way through and leaks on the floor.  Basically this would mean that you need to replace the tank with a new one.  That is of course if this is a new problem.

If your water has always been yellow, you may have rusty pipes under the house or just yellow water in which case you would need a filtration unit/water softener.