The situation has worsened because the two main service reservoirs will have emptied as well as the trunk mains coming down the valley. Some smaller distribution zones such as Pydew, parts of Upper Colwyn Bay and the Great Orme have their own service reservoirs so, potentially, could last out a bit longer.
Many lessons need to be learned from this debacle not least around security of supply for such a large distribution area (much increased in extent as smaller, independent sources have been abandoned) which apparently is now entirely reliant on one feeder pipe routed, for some reason, deep below a stream and only installed within the last 15 years. Nothing to do with lack of investment or aging infrastructure.
Come back Conway Valley Water Board!