Carl's idea is a great one (wish I'd thought of it!). If you were to add one pound of 65% Cal-Hypo to your 15,100 gallon pool, it would increase the Free Chlorine (FC) by 5.1 ppm and would also increase the Calcium Hardness (CH) by 3.6 ppm. Though it won't get your calcium up quickly at least it's in the right direction and it does give you the option of another chlorine source -- one that is sometimes less expensive than liquid chlorine.

Richard