One of the common pathogens of p-valve associated UTIs is uncommon in other settings, and that is Pseudomonas. This particular bug is not deterred well by alcohol, but is intolerant of low pH, so a half-and-half mixture of vinegar and alcohol is a pretty good antiseptic. But, as we say in surgery, the solution to pollution is dilution -- before treating the system with disinfectant, flush it with copious amounts of clean water.
In addition, be diligent about hose routing to avoid kinks. It seems that one of the risk factors for UTI is backwash -- when the diver attempts to urinate and encounters a blockage, there is back pressure that can push bacteria up the relatively long male urethra (which is what protects men in general from UTIs).