How do I break chlorine lock?
One of the main reasons that chlorine can become "locked" is that too much stabilizer has accumulated over the course of time. Stabilizer (cyanuric acid) can build up over a long period of time, sometimes months or even years. Once the stabilizer reaches high levels, the chlorine in the water is useless. The only way to break the lock is to reduce the level of cyanuric acid in the pool. The quickest way to do this is to add fresh water to the pool. This will help dilute the acid levels in the pool so that the chlorine will become more effective. Pools should be partially drained and refilled (every 3 years or so).
Following chemical treatment, how long do I have to wait before I use my pool?
With the exception of superchlorinating (which requires waiting until the chlorine level drops to recommended levels), you can generally use your pool when the chemical is dispersed throughout the pool. Fifteen minutes to one hour is a good rule of thumb.