Since 2001, Welsh Water has been owned, financed and managed by Glas Cymru. Unique in the water and sewerage sector, Glas Cymru is a company limited by guarantee and as such has no shareholders.
The Glas Cymru business model aims to reduce Welsh Water’s asset financing cost, the water industry's single biggest cost.
Under Glas Cymru’s ownership, Welsh Water's assets and capital investment are financed by bonds and retained financial surpluses.
(From Welsh Water website).
I’m not sure if this is the sort of model you are thinking of Monica? As Callistemon21 said, Welsh Water is not without issues, although it does consistently perform as well as, or better than other water companies. The biggest issues seem to be that the infrastructure is outdated, and revenue is insufficient to invest to future-proof for the effect of climate change. Hence overspill into rivers and the sea when there is flooding, and burst pipe wastage. Obviously very rural places have high infrastructure costs, and mountains create lots of water, so it’s not all down to things under their control.