My dad is 84 he sits with feet up has them up in bed on a wedge but his left leg still swells docs don't like to keep him on water tablets as kidneys ?

If only one leg: Swells, and the swelling doesn't seem to go down with elevation, chances are there is something else causing the swelling in that leg beyond fluid retention. There are a number of things that could cause unilateral swelling, and any fluid retention dad has will make it look worse. It's important to have dad checked by his doctor for something locally going on to cause the swelling on the left.