The problem is that the organic nitrogen in the urine reacts with the chlorine in the pool to form chloramine, which is more irritating to eyes and skin than wh

The problem is that the organic nitrogen in the urine reacts with the chlorine in the pool to form chloramine, which is more irritating to eyes and skin than what was in the pool before--probably hypochlorites (NaClO, Ca(ClO)2, or LiClO) with cyanuric acid UV-stabilizer--and less effective at killing bacteria. By peeing in the pool, you are using up the sterilization capacity already present in the water. The water quality manager then has to increase the rate of chlorination far past what is strictly necessary for bacteria, sweat, skin dust, and sunblock, to account for all the pool-pissers. With over-chlorination and a good particulate filter, some amount of pee in the pool can be absorbed by the system. But if you have the capability to exit the pool and pee in a toilet, that is the civilized and courteous thing to do. If you recognize NaClO above, you might also know it as bleach. And you might also know that it is very dangerous to mix ammonia with bleach, because it forms respiratory irritants like chloramines and cyanogen chloride. The same types of reactions can occur with the urea in urine. Also, urine can fertilize algae growth in the pool and screw up your pool pH.