To Change or Not to Change...

Here's a question. Let's say, hypothetically of course :), that you have two small children in the bathtub. One pees in the water at the beginning of the bath. The other one thinks its funny and pees in the water also. Do you:

1) bath them in the pee and say "oh well, pee is sterile"
2) change the water immediately
3) Decide that you will only change the water if there are floaters in the bathtub (and by floaters I mean poop).

I'll see if I can add this as a poll and see what people think.