I've read on a forum that someone has used these in a water bladder and that a lot of gas is initially released, so I suppose the answer is yes. I intend to use them in this way. I can imagine excess pressure when you bite on the valve the very first time so would probably avoid problems by squeezing with fingers and aiming it away - some liquid will of course be wasted in this way. The other alternative would be to only fill the bladder say two thirds full so that the pressure can be taken up within the bladder. Sorry all this is only theory.