Cicero wrote:
I'm well aware of the several uses for a cold water storage tank
(plenty still in use) but it was the quite limited use described by
Ophelia that prompted my question. If the cold water tank serves only
one bathroom with possibly infrequent use then it might become
stagnant and could be unsafe for emergency use - particularly for
drinking, teeth cleaning etc.

We never use that bathroom for anything other than the loo really and of
course the handwashing, especially after working in the garden..