pH of pure water at room temperature is 7. The dissociation constant, KW, has a value of 1.0*10−14 at 25 °C, so in neutral solution both the hydrogen ion concentration and hydroxide ion concentration are 1.0*10−7 mol/L.
The pH value of pure water decreases with increasing temperatures because the dissociation constant, KW, is depending on the temperature: 7.94*10-14. So the pH of pure water at 50 °C is 6.55. At that temperature both H+ and OH- concentrations are 2.8*10-7 mol/L