Actually, most of the places I have been either have or are switching to Sodium HypoChlorite, reason being that Gaseos Chlorine is just damned dangerous. Granulated or Puck form chlorine (Calcium HypoChlorite) is used at a couple of our well sites and on new installations of mains and services due to its relative long term stability and ease of use. Sodium HypoChlorite, in the form that we get for Water Treatment is 12.5% vs your normal over the counter bleach being 2%-3% chlorine. Sodium HypoChlorite loses strength over time but the risks are SO much lower that it is fast becoming the if not already the preferred method of chlorination for groundwater. Surface water on the other hand is often switching to a process called Chloramination due to the fact that Chloramine's do not have the Disinfection Byproduct of Trihalomethanes which is a known cancer causing agent. In short, I would go with the simple method, use bleach, don't try to use other pool chemicals or what have you, bleach is safe, readily available, and cheap. Also I would suggest ordering some simple total chlorine test strips such as http://a.co/bmNyePI to use when you first hook up in order to make sure that the water you are getting has been chlorinated, the reason I say to use total instead of free test strips is because if Chloramination is done correctly there should be no free chlorine. Anyhow, this was my first post here I hope it was useful to someone.
PS I am not a chemist, but I am a Water Treatment Plant Operator
