At D-I Supply, they really listen to your needs, take time to test your water, in order to provide you with exactly what you need at an affordable cost. When working on a low budget, they helped me determine exactly what I HAD to have, then recommended what to follow up with, in order to keep my pool "afloat" during a hard time, until I could care for it consistently again. Thanks to the people at D-I I can now do my back exercises in a beautiful, clear-water pool instead of what was starting to have the characteristics of a pond. If you are attempting to maintain via department stores, and think you're saving...add the cost over 2 months, then go to D-I for two months and compare. Why save a couple dollars to repeatedly guess, when you can go to an expert who can guide you. It would be like going to the pharmacy when sick instead of the doctor, and purchasing different meds until you hit the one that cures right illness.