[mrmikey]

It does sound like water but it could be air. If the suction side of the pump has a loose fitting or if the fluid is low it'll become aeriated, (the air will make small bubbles and turn white)
Take some of the white fluid out (using a turkey baster for example) and put it in a clear bottle and don't move it for a day or so. If there's water it'll settle to the bottom of the bottle.
You'd have to be ....ahhhhh....pretty dense to add water to a ps resevoir considering the ww resevoir is usually blue and a far sight easier to get to compared to the ps resevoir....Mike