Water Storage: (Large)Swimming Pools

From Homeland Security

http://www.nationalterroralert.com/safewater/

(Snip) ... Using Swimming Pool Water

You should always view your pool as “backup” water; keep the water treated; you never know when it will be needed! The maintenance of the free chlorine residual will prevent establishment of any microorganisms. The maintenance level should be kept about 3-5ppm free chlorine. (See Water Purification for detailed information on purifying pool water.) If other stored water stocks are not available, remove the necessary pool water and boil it or just treat with chlorine to the normal 5ppm. It is best to err on the side of caution.

Covering the pool at all times when not in use is a very good idea. Try to keep the cover clean and wash the area you put it on when removing it from the pool.

Finally, a few words about using swimming pool water.
http://www.aquatechnology.net/Emergency_Storage.html

If you(or your neighbor) own a pool, you should always view the pool water as "backup water"; keep the water treated; you never know when it might be needed.

The maintenance of the free chlorine residual will prevent establishment of significant growths of micro-organisms. The maintenance level should be kept around 3-5 parts per million(ppm) of free chlorine. Use your chlorine tester to monitor this. If you don't have one, visit your local pool supply company soon.

The principal problem with using swimming pool water is that organics can enter through dirt, sweat, body oils and the inevitable kiddie tinkle. This can form carcinogenic(cancer causing) chloramines(e.g. chloroform) which are not good to drink. In a survival or emergency situation, steps can be taken to minimize or completely eliminate such contaminants.

Partial and complete water changes should be done when possible. Although it is impossible to make a general rule, change the pool water at least 1-2 times per year and make partial changes after a lot of use.

In a sealed drum, water can stay good for years, but we still recommend changing it at least once a year. Now, imagine going in and out of your emergency(pool) water a hundred times and then drinking it. Don't let pool water clarity fool you---some crystal clear mountain springs have tested out to be laced with cholera, Giardia and Cryptosporidium parasites.

Drinking Swimming Pool Water in an Emergency | Safe To Drink?
https://modernsurvivalblog.com/preps/drinking-swimming-pool-water-in-an-emergency/

  (SNIP) ... The notion of relying upon swimming pool water for a backup source has flaws and caveats. City dwellers will not find many residential pools nearby. Swimming pools are more concentrated in geographical areas with a hotter climate. They are more often found in areas where people can afford the luxury. Additionally, one cannot assume that all swimming pools have been treated such that it’s safe to drink pool water… ---CONTINUED---

How To Use Swimming Pool Water In An Emergency
http://tinhatranch.com/use-swimming-pool-water-emergency/#.YCWJJWNOmu4

  A person new to preparedness recently contacted me with a bunch of questions about how they could better prepare for a disaster or SHTF.  One of the questions was concerning the pool they had in their backyard, namely, was the water safe to drink.  Pools are wonderful preparedness items.  How else can you efficiently store ten thousand or more gallons of water?  Yet, there are many questions that need to be answered in some folks mind’s.  Let’s take a nice logical look at why a pool is a good water storage device for SHTF, as long as you understand a few things. ---CONTINUED---