I'm not aware of any toxicity to drinking the chemicals in a properly maintained, chlorinated pool for a relatively short period of time (i.e. not months or years). I have no idea about the safety of pools that use other disinfectants besides chlorine. You often run across admonishments to not drink pool water, but I suspect that the warning is aimed at curbing gastrointestinal illness and not because pool water is poisonous. In everyday life, yes, don't drink pool water. You can get sick. Why risk getting sick when you can just walk over to the water fountain for a drink of water?
But in an emergency, I think it is OK, although it may irritate your gut. However, you should assume that the water needs treatment since normal chlorination may keep the water clear and algae-free, but it won't necessarily kill all the bugs that may make you sick. I would definitely treat water from a public pool or any pool that gets a lot of use. An emergency is not a time to play Russian roulette with your health by drinking untreated pool water.
If a pool is going to be used as a water source, then it should really be tightly controlled to prevent additional contamination after some disaster. No more swimming, cover it to keep organic debris out, don't let pets drink directly from the pool, don't bathe or wash dishes near the pool so that waste water drains into the pool, don't dip potentially contaminated buckets into the water, etc. Any contamination would, of course, be diluted by the large volume of water, but then again, the pool likely won't be filtered and maintained after a disaster starts, so its best to minimize further contamination.