By Ali Lyon Ofwat is opening enforcement cases into four more water companies, meaning it is now investigating every single water and wastewater firm in England and Wales for the mismanagement of their networks and treatment. On Tuesday the regulator confirmed it has served formal notices on Dŵr Cymru Welsh Water, Hafren Dyfrdwy, Severn Trent and United Utilities to gather evidence for the investigation. The notices follow a what Ofwat described as a “detailed” analysis of information on firms’ environmental performance and data about the regularity of their spills from storm overflows. The re…