Chloramine
That is likely because your water is treated with chloramine, which is a compound of chlorine and ammonia. When you treat the water, it frees up the ammonia and you will detect it in your test.
Ms.Bubbles said:Yep, that's the one I've got. I like the 2-part ammonia test-- I find it much more accurate than the 1-part Hagen test, which always gave my dechlorinated water a positive ammonia areading, even when there were no fish in the tank.
That is likely because your water is treated with chloramine, which is a compound of chlorine and ammonia. When you treat the water, it frees up the ammonia and you will detect it in your test.