The average public swimming pool contains 75 litres of urine..
Well if the pool, lets say, is 50m x 20m x 2m that is only 0,0000375 or 0,00375% .
That's taking the piss!
More like adding the piss...
Urine isn't the most pleasant thing in the world but it's far from toxic. Mostly water, salts, urea and minerals. I wouldn't drink urine because that's disgusting but at the same time, it wouldn't hurt me if I did..