How/Where to Install chlorinator

[rtpatter]

Sorry to hear about your dog I hope she is feeling better. As far as the installation what type of drill bit to use to drill the holes "(a standard 3/8" bit)? Also most importantly based on my attached picture above where to I need to drill the 2holes? I think the return line is the one with the 2 paint stain droppings on it. I would think I would need to drill one of the holes close to that. However, based on the diagram I have seen one hole needs to be drilled in the line that goes from the pool pump to the filter. In my situation I have a flexible tube that goes from the the pump to the filter so I'm not sure if I can drill a hole into that. If I can drill into the tubing where do I put the hole.

Any advice appreciated.