So first let me begin by telling you about my pool and its problems. It is an 18,240 gallon in ground pool with a DE filter and vinyl liner. Some things came up in my life last year and I quite stupidly did not cover my pool for the winter. This season the pool was extremely green and after getting the filter running I balanced the chemicals with the advice of the pool store. Currently my readings are FC=0, pH=7.0, TA=120, CA=90, CYA=27. So I proceeded to shock it with 70% chlorine pool store calcium-hypochorite shock from Leslies. Well, I put two bags in last night and I brought the pool water in for testing once again and the pool guy said that the reason the chlorine was not showing up was that there was chlorine block or lock and I had to "burn out" the pool by adding 5 bags of 70% calcium-hypochorite. Should I do this or is the pool guy just trying to get my money (I already have the shock)? I know I should buy my own test kit but for now should I just "burn out" the pool? I should be using bleach and I have bought numerous jugs but should I wait to use that when I am maintaining the pool chlorine levels?