Charlene Wallace, the former customer services director at Monarch Airlines, will oversee teams responsible for customer service, metering and billing, and data.
The Water Bill is expected to receive Royal Assent at Westminster in April, thereby paving the way for the opening of a competitive water retail market in England from 2017.
Mark Powles, chief executive of Business Stream, said: “Charlene brings a wealth of experience and history of innovation with her to Business Stream, and will play a key role in our expansion to new markets. She understands our vision of becoming the gold standard for customer service and is already contributing to this with fresh insights on a range of areas we are addressing.”