Chlorine is a consumable, like gas in the car or food for the dog. What is consumed each day by the hot sun or by killing algae and bacteria must be added back. Most users here will add chlorine every day to maintain their required level. With a CYA level of about 40 you should keep about 4-7ppm of FC and never let it fall below 3.
The best way is to test about the same time each evening and add the required dose to get back up to target range. The key is to add enough so that by the same time the next evening you are still above your minimum of 3. Just be aware a lot of swimmers in the pool will introduce extra bacteria to kill and will increase your chlorine demand. If you add a whole bunch of chlorine at once the extra above your stabilizer level, it just quickly burns away.
You must have some stabilizer because without it, ALL your chlorine will rapidly burn away in the bright sun and warm water temps. A CYA level of about 40ppm is best for a pool subject to intense sun. The key is to not add too much. Tablets and granular shock get folks in trouble because they continually dose stabilizer into the water and it quickly builds up, gets too high and blocks the chlorine from working. Liquid chlorine bleach is the answer, it will not add anything but chlorine, water and a little bit of salt.
Accurate test results, regular dosing and a few simple daily chores will have your pool beautiful, clean and safe for the entire summer. A few minutes to test, dose and clean the skimmer basket, it takes about 5 minutes. Add a few extra minutes on the weekend to brush the walls and floor and the pool just stays crystal clear. Ignore it or try to shortcut and the green monster will come out. You will sweat, scrub, test and buy cases of bleach to bring it back. It's much easier and more fun to just maintain it!!
