You can take the "purest" water on the planet and if you store it in glass it will leach minerals from the glass. If you store it in plastic, it will leach plastisizers from the plastic. In both cases it will absorb carbon dioxide from the air, lowering its pH. Having "pure" water when I was a chemistry student in analytical lab was a bitch! Depended on whether you could live with ionic or organic contamenents. If you needed neutral pH that was another matter. Good distilled water should suffice for cleaning records. Going to heroic lengths to purify it seems pointless.
