In this way you will be able to use it more effectively and for a lot more.
Whether you need to convey that a lifeguard is not on duty or there's chlorine content in swimming water, a symptom can do all this.

Maintenance should be the priority of the pool consumer.
While low levels of chlorine, on the other hand, can trigger algae spreading. When employing a torch to change flies, unhook a trout etc, it could be ruin your night vision, and although it 5-10 minutes for it to use it again.