Why does water go off?

12 January 2016

Question

Why does water "go off", and how can you store clean water without it spoiling?
If I leave some dishwater in the sink overnight, or leave pee in the loo for a long period of time it can smell quite lethal. Why is this?
Does water in springs or wells go off in this same way?
I read an article on a tsunami relief project where the Earthship people were building water tanks/rain catchers in villages. How long does the water remain viable? And do you have to add anything to the well? Does adding an alkaline, or fish to water tanks help?
I want to recycle bath water in my garden. Reading some grey water web links, grey water storing is strongly discouraged, because pathogens supposedly multiply and can be harmful. Why is it safe to put immediately on the garden but not store it?
How is water stored/recycled on boats/liners, trains, space ships etc?

Answer

Kat Arney put this question to chemist Ben Pilgrim...

Ben - It's almost always because there's something in it. I mean water is an inherently stable molecule. In fact, they've found water that's 2.6 billion years old, sort of buried deep under the ground in Canada and nothing's happened to that. The problem is that if there are small contaminants within the water molecules, sort of microbes, things like that. Then, over time, if they have the right conditions these microbes can sort of grow and proliferate, and make toxins, and so on.

Kat - So it's not the water - it's the stuff in it!

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