cbuchin, Your pool dealer is getting his information from the people who sell him the chemicals to put in his store. While he may not be aware of giving you any wrong information he is. You have to be careful of learning from someone who is selling you something. It is like I always say.... you can find a poll that matches your way of thinking - it is all about what questions you ask. It even goes as far as the salesmen are learning from the companies they sell for so they are believable because they are telling the truth as they know it. The thing about this forum is that the information is put here by people who have learned how chemistry affects swimming pools, and from experience. If you read through the forum you will see that we always ask for feedback on what worked and didn't work. The forum is a place that you can go to get information from regular people who have had pools and taken care of them for many years.