Northern Ireland Water has paid out more than £3m in legal fees since 2007.
The company said the costs are comparable to those of similar organisations.
The government-owned company said its legal fees reflect the varied and complex nature of the operations it undertakes.
The figures were revealed in answer to an assembly question from the SDLP MLA, John Dallat.
The legal bill at Northern Ireland Water is close to £1m in this current financial year, according to figures obtained by John Dallat.
Legal fees were close to half a million pounds in 2007/8, more than twice that the following year, and around £800,000 last year.
When this year's figures are included, the total is around £3.3m.
Mr Dallat has questioned whether this is value for money and wants to know how much was spent seeking legal advice to sack employees or extricate the company from what he called "stupid contracts which have tied up millions in public money".
The government-owned company said its legal fees reflect the varied and complex nature of the operations it undertakes, which include its legal and regulatory obligations.