Northern Ireland Water is asking for the public's help in finding businesses and farmers who do not pay for their water.
Ways of stealing water include unauthorised connections to the public water main, misusing domestic water supplies and bypassing water meters.
Culprits could face heavy fines, a large legal bill, and a bill for the water that they do not pay for.
The company says most people do not realise water theft affects them.
"The illegal activity is generally carried out to evade payment of non-domestic water bills, which is basically fraud," NI Water's Dr Gary Curran said.
"This reckless behaviour also increases the risk of contamination to the public water supply and therefore a significant risk to public health. Therefore, it does affect us all."
'Resource and effort'
The Consumer Council is supporting the campaign.
"We would encourage all consumers to report suspicious activity or known incidents of water theft, to the hotline, in order for the appropriate action to be taken," the council's Graham Smith said.
It has also been welcomed by the Utlity Regulator.
"The Utility Regulator recognises the range of issues that can result from this sort of activity and welcomes any action taken by NI Water to prevent this and to recover costs where appropriate," the regulator's Paul Stewart said.
"A lot of resource and effort is invested in the collection, treatment and delivery of high quality water, therefore this will ultimately help benefit and protect consumers and the environment as a whole."
A confidential hotline has been set up for people to report water theft. the number is 03457 440088.