It is possible to have too much of a good thing. It turns out that water, the liquid that keeps you alive, can also poison you.
One poor woman in the UK found out the hard way when she started noticing symptoms of a UTI, and thought she could "flush it out" of her system. Pro tip: This is why doctors exist, so you don't have to DIY a treatment plan. She started drinking more than a cup of water every 30 minutes to treat the urinary tract infection, but ended up hospitalized. Talk about a backfire.
The patient had dangerously low levels of salt in her blood, a condition called hyponatremia, more commonly known as water intoxication. This happens when people drink so much water, it dilutes their blood of important nutrients like salt and electrolytes. It can create swelling of brain cells, and symptoms include disorientation, headaches, nausea, and vomiting. If sodium levels dip too low, it can even lead to death -- much more serious than a UTI, medically speaking.
As the woman's condition progressed in the hospital, she vomited a few times and had difficulty speaking. Her sodium level was at 123 millimoles per liter, and anything below 125 mmol/L is considered deadly. Luckily, doctors reduced her fluid intake and she was released from the hospital the following day.
People poisoning themselves with water happens more often than you think
Ironically, water intoxication occurs most frequently among ultradistance athletes, people who presumably sweat a lot and need to replenish their fluids. They'll sometimes drink way too much water in preparation for training or a competition, diluting their sodium levels.
It's understandable why someone would accidentally poison themselves with too much water. You constantly hear about the importance of drinking plenty of fluids; it's tied to everything from having more energy to weight loss, and it's emphasized even more when people are exercising or are sick.
A better rule of thumb is to stick to the recommended 64oz of water a day, or about 8oz every hour. Even during intense exercise, people should only drink about 6oz every 20-30 minutes. It's also important to pay attention to your body; if you notice the symptoms of not drinking enough water, then fuel up.
Moral of the story: Don't overload your system with H2O just because you think it will be healthy, and definitely don't try to flush any type of infection from your body. In addition to frequent bathroom trips, you may end up with a trip to the hospital.