I would be interested to know why you believe tap water is not 'sanitary'.
The UK has one of the safest tap waters in the world.
I brew with mains water.
I use it to rinse.
And importantly I drink it straight from the tap, and have done all my life. Millions of others in the UK are the same.
The provision of tap water in the UK must meet the EU Drinking Water Directive which leads me to a quote from the Water UK site.....
The law requires that drinking water is wholesome and clean. It sets down maximum acceptable concentrations for a number of potential contaminants. In addition, there is a general clause, which requires:
"Water is free from any micro-organisms and parasites and from any substances which, in numbers or concentrations, constitute a potential danger to human health"