One in four people in the UK rely on Thames for their supply and its customers are facing a steep rise in bills.
In July, the company had told water regulator Ofwat that it wanted to increase annual bills by 23% between 2025 and 2030.
Since then, Thames has said it needed to raise them by 53%.
The BBC understands there are up to six parties interested in taking a stake in Thames Water.
This would happen once the firm’s existing investors have agreed how much of the debt owed to them they are willing to write off and there is greater clarity on by how much Thames can raise household bills.
Potential future investors include Castle Water, the UK’s largest independent business water retailer, which acquired Thames’ business customer operation in 2017.
Castle Water was founded by Graham Edwards, who is the Conservative party’s treasurer and has donated millions of pounds to it over the years. Mr Edwards is also a shareholder and director at Castle Water.
Other possible buyers include Brookfield Asset Management, the Canadian investment giant chaired by the former Bank of England governor Mark Carney and Hong Kong’s CKI which already owns a stake in Northumbrian Water.
Chris Weston, chief executive of Thames, which has £16bn worth of debt, said that the new loan has put the firm “onto a more stable financial footing as we seek a long-term solution to our financial resilience”.
The company’s debt will swell to £17.9bn by the end of next March, it confirmed on Friday.
Its finance chief Alastair Cochran said that the UK government is aware of the firm’s position and has kept in close contact during the negotiations over the new loan.
The water industry as a whole is under pressure to improve. Customers’ bills have been rising – and will continue to do so – but sewage spills into England’s lakes, rivers and seas, for example, doubled last year.
