Pure Water Storage ?

Hi guys

my question is once I purify my water how long does it stay pure and useable for window cleaning? will it go manky like normal water does after standing along time or does it always stay pure ???

I was wanting to store some in a bog standard garden water butt too will it be ok stored in this way or will it get contaminated etc??

Thanks all

PS if I was to use normal water tanks instead where can I get 200 to 400 ltr ones at the very best prices and compact ones if possible to store round the back of my shed in small back garden etc?

pure will stay pure for quite a long time in a water butt. However if you use a clear plastic tank the tank will start to go green inside and eventualy you will get wiggly things in it too but the water could still come out pure 000 ppm. /emoticons/biggrin.png