The number of households on social tariffs has risen by a fifth since last year to a record 1.6 million. Spending on them rose by a quarter, according to CCW data.
It said the increase was down to companies doing more to promote their support schemes, data sharing between the government and councils helping to identify customers in need, and the cost of living leading to more households seeking help.
But there are concerns that support is not the same across the country and that people could be missing out on help simply because of where they live.
Each company’s social tariff scheme differs based on things like household income, benefits received, individual water bills and how much people have in savings.