Use a hosepipe in a garden or for cleaning walls or windows of domestic premises, paths or patios, a private leisure boat or an artificial outdoor surface, where such use is necessary for health and safety reasons;
Use a hosepipe in the course of a business to clean a private motor vehicle, or for cleaning walls or windows of domestic premises, paths or patios or an artificial outdoor surface, where this is done as a service to customers
Taken from Anglian Waters Web Site "What am I still allowed to do"