Is this the correct blue color? I realized I've been doing it wrong after reading posts on here about it. I was reading it at purple. So I went to blue this time and my number went way up to 725. At what level should we drain it? Is draining the only way to get the CH level down? We've only had the pool since February and we even had to drain some water off because of rain. I'm not real keen on replacing water every 6 months.