From time to time there are problems, such as a blockage at the inlet to the tank or (very rarely) drought, or a leak, open hosepipe, or excessively heavy use which drains the tank. The supply to some houses can also freeze in very severe winters. But the community, working together, usually sorts out these problems within a day.
Responsibility for the supply is complex. The supply was established to serve the crofts, and private, decrofted properties which have been connected since don't seem to have any right on it, though most are supplied. The authorities, such as Scottish Water, seem to have no interest whatsoever, except they do test supplies on private supplies - at the property owner's expense. So it's left to the community, and this isn't easy since different members have different demands. For example, the whole system probably needs a thorough upgrade, but this is expensive and will not, therefore, be supported by those who have a smaller demand. Some members of the community feel that government, at whatever level, should intervene to ensure that all communities, however small, are served by a reliable, clean water supply - which is, after all, what the rest us expect.