Treating water doesn't remove the chemicals. You are treating only to keep pathogens like cysts, amoebas, bacteria and viruses from causing you illness. I wouldn't want to bathe in chemically treated water either. You could use it for toilets, however.
You may have little or no space above the suspended ceiling. However, if you do have sufficient space, a small shelf suspended above the false ceiling and anchored into the supports would give you a place to hide items that might be of more value and certainly items you would not require constant access to. I would pick a location in a corner of the room so you would have two walls to help support as opposed to the middle of the room, for example. I would want to construct the shelf so it has some ability to secure items. You certainly wouldn't want things shaking loose in an earthquake and come crashing down through the ceiling. Perhaps a ledge around the exposed edge of the shelf to keep thing from sliding off. Just a thought but any area that you can use and would be hidden would be to your advantage.
Something similar to this:
http://www.josephdcook.com/images/shelves.jpg
You can see the small lip in the next picture. That's what I meant to keep things from sliding off.
http://www.racingproducts.biz/RPpics/Shelf_Lip.jpg
