I'll probably catch heck for saying this, but the only time I sanitized our water system was when it was new. We are into our 4th season and have had no issues. Its never had anything but non-municipal water in it, for whatever that's worth. I always figured there was enough chlorine in it to not have to worry about it.
2013 Roo 183
2012: 1042 Miles, 13 Nights camped
2013: 2772 Miles, 27 Nights camped
2014: 2259 Miles, 30 Nights camped
2015: 1644 Miles, 20 Nights camped
2016: 550 Miles, 11 Nights camped