I would suspect that your reading of the level was a little low, so you did not get the dilutional effect you were looking for. You need to use a quality liquid reagent FW
test kit, such as sold by aquarium pharmaceuticals (about $15 online, $30 + at your lfs
) Test strips are notoriously inaccurate and lead to confusing results.
Or, you could have chloramines in your water. If you have 0.5ppm or higher of chloramines, then you would not get much if any dilution of the ammonia level of 1 ppm
(since chloramine is converted to ammonia by dechlorinators). The city of chicago has a seperate water supply than the suburbs, I beleive. I don't have chloramine out here in dupage county, but I don't know about chicago. You can look up the report online. Or you can test your tap water. If you use a two bottle, salicylate ammonia test and you have chloramine, it should turn color.