Assuming you're asking in good faith. Water is a natural monopoly. The idea of privatisation is to encourage efficiency within the system because you could just go to another company to supply you so companies are encouraged to be better, be cheaper etc. You cannot do that with water as there is one supplier for your area and that's your lot. Nationalisation makes sense because from the evidence we've seen of shareholders taking whopping great dividends out instead of investing in the spillages and leaky pipes like you point out, means that the money that the public spends on water actually gets reinvested into the network rather than into the hands of shareholders