In a dire pinch, it would be drinkable, provided your pool is not a mosquito breeding pond when you dip your laddle (not clear).
However--your pool is 20 to 30 thousand gallons of stored water.
You only need a way to filter or purify it. Your best bet would be to have one of those membrane filtration systems (a large size one) that can produce hundreds of gallons before the membrane needs to be replaced.
These type of systems take out nearly everything even viruses.
Barring a membrane system... distillation. And you wold have to rig up something akin to a whiskey still, and have a large amount of fuel (wood, oil) to keep this thing running.
If your pool water is clear, you can use it for washing and cleaning--but not for the final rinsing of eating plates, utensils, or pots and pans... these have to have a clean (safe) water rinse, or a rinse (dip military style) in boiling water.
The membrane systems are best--however you do not want to be hand-pumping the bugger for endless hours. A solar rig on a battery, or a stationary bike with the wheel connected to a belt which runs the pump should be MacGyver'd together.
I think in a bug-in scenario, or natural disaster--you have a big, big edge with a pool.
One last bit... if you do plan on using this thing as an emergency water supply--have a pool cover on hand. You will want to protect it from bird defication, bathing, dust and contaminants, etc. Also you will have to guard it from your neighbors... unless they can provide ample alcahol or steaks for the que.
T