You really need to get a better test kit. Walmart has one for about $ 15.

This kit will test for free chlorine and total chlorine. When you know both of these numbers you subract free from total and it tells you what you "combined chlorine" level is.

Combined chlorine is chlorine that has been partially used oxodizing stuff in the water. The stuff could be just leaves and debris, or kids pee and fecal matter. The fecal matter is where there dangerous infections come from. This is why you need to know the combined chlorine ( shorthand CC ).

If you discover you have a CC level of 0.5 or more then there is "stuff" in the pool that needs to be oxodized to sanitize the pool. If you keep adding regular doses of chlorine, you will not attack the CC. You need to raise the level of chlorine to shock levels to burn it out.

What the shock level is in your pool will depend on the CYA level ... another reason you need a better test kit. See the article at the very top of this section "best guest CYA" That will give you more info.