John

Thanks for the reply to this thread.
I use a swimming pool version of chlorine plus a carbon particle filter and monitor the ph & Cl levels so it is fine for us. As you say you can smell chlorine if there is a blast of water into a bowl, but not otherwise
My concern with chlorine is only about it reducing the effectiveness of the septic tank (where all our tap water goes). Do you think that is a reasonable concern?

I am not sure how the Cal option works  and what levels it needs to be effective. It is the traditional method in many parts of Europe and I hoped it would not have the same impact on our septic tank. Any thoughts?

Cheers