Valerian Root extract has a mild antibiotic effect, but I don't know whether it is safe for dogs. I used it for my own UTI a few years ago and it worked like a charm, but it is quite bitter. You might be able to hide a drop or two in his water for prevention, but please check on safety first.
@nobarkus:
When he pees though he'll stand there for a long time and I'm thinking where does all that water come from?!
Does Buddy drink from the freshest and best smelling water in the house….the toilet? I know AJ does, every chance he gets when we're in a hotel room...like I don't put fresh water down for him. I have to keep the lid down or the door closed.