How long is it safe to leave fresh water in tank?

[aberglas]

Water in household rainwater tanks can stay there for years, no problem. Never had chlorine in it, leaves, some bird pooh.



That said, some municipal supplies rely on lots of chlorine to keep them safe, that that chlorine dissipates over time, which is why the water tastes better after a rest.

I do wonder about water from third world countries though.