If your chlorine reads 3, then you need to add more chlorine til it gets back up to 15.

In order to read higher than 5 with your kit, use one part pool water to one part distilled water, mix well, test from that sample, read results, then multiply by 2. If it's still reading higher than your highest, then use 1:2 and multiply by 3. You'll lose a little accuracy with each dilution, but it's still better than estimating, and maintaining shock level is the only way you're going to get your pool cleared up.

Janet