I'm not sure exactly what you mean by "water infection" but assume your mean a urinary tract infection. I completed radiation treatment last week. Over the weekend I started having to pee way too often and also had pain when urinating. I've had UTIs in the past, but this felt different, largely because the pain was worse and felt more on the outside, if that makes any sense. I also had this itching that grew worse every hour it seemed. I thought the worst, of course. I sent my oncologist an email telling her of my symptoms. She responded (Sunday!) and asked a bunch of questions. She told me that it was most probably a reaction to the radiation, but to be sure she asked me to go to the local hospital where she would arrange a urinalysis to rule in or out on the UTI. I have no faith in our local hospital (long story) but she assured me that she would have her own experts review the results. Anyway, it turned out to be a UTI but a bit different from the standard UTIs. (I still have no idea what she meant...) I am on an antibiotic and a topical ointment that is helping a lot. As always, it's best to check with your own doctor ASAP. Everyone is different and what happened with me may not be true in your case.

Incidentally, I'm, going to add this because I think it is important and because it took me too long to learn this lesson. If you do not feel comfortable calling/texting/emailing your doctor with a question regardless of time or day, then I would urge you to find a doctor with whom you feel more confident and comfortable. It took going through medical hell for me to grasp this idea.