It's fairly cheap, and I use such a small amount of it in general (I guess if I used a citric acid stop, I'd use more) that I have no reservations about using it occasionally to descale my espresso machine, which reminds me--if you're in a pinch until your order arrives from PF, you could see if your local grocery or cookware shop sells powder for descaling coffee makers, which is usually just citric acid, but it's much more expensive to buy it in little packets that way in the long run.