Contrary to popular belief, the pH of urine is actually light acidic, in the range of 4.5 to 6.5  The kidneys maintain normal acid-base balance primarily through reabsorption of sodium and tubular secretion of hydrogen and ammonium ions. Urine becomes increasingly acidic as the amount of sodium and excess acid retained by the body increases. Alkaline urine, usually containing bicarbonate-carbonic acid buffer, is normally excreted when there is an excess of base or alkali in the body.  Some medications for urinary infection work best on alkaline urine but this is not typical of a healthy adult who is not taking any medication.    In a typical diaper, it is possible to see an increase in the pH value.  As urine biodegrades due to time and oxidation, ammonium hydroxide is generated, increasing the pH values to 8, 9 or as high as 10 (generating a hazardous condition known as "diaper ammonia dermatitis".    In addition, it is well known that superabsorbent performance is reduced due to the higher pH, making it even worse for the patient.   Diaper should be changed before there is a risk of diaper rash associated with ammonia. Diapers should not be used for more than 8 hours at a time without a change. Diaper with feces should be immediately removed.