If you have become aware that there is water leaking in the roadway, sidewalk or on your property, it is important to first call 311 and report the leak including all of the details you are experiencing. The 311 call center will document and report all of the details to the Department of Environmental Protection.
An employee from the DEP field unit will start the investigation process by making a visit to the location of the leak for a visual observation. Please do not be alarmed and feel confident that you are doing the right thing by notifying the city. DEP is not going to show up and turn your water off out of nowhere unless there is a major leak that is creating a dangerous situation.
The DEP field unit will begin the process by checking the water mains of all neighboring houses. It may take some time to gain access but rest assured, they will complete a thorough investigation and determine where the leak is coming from.
If it has been determined that your main is leaking and you have been issued a three day notice it is important to contact a licensed master plumber to assist in a second opinion, and resolving the leak by replacing your water main. It is important to understand that the plumber must specialize in sub surface water main repairs, hold a special bond with the NYC Department of Transportation and all of the required insurances to excavate in the roadway.
If you suspect that the leak is yours and is worsening, you can call the licensed plumber to come out and investigate prior to DEP. There is no true downside for having the plumber investigate and he may even feel confident concluding on a source for the leak. In a case like this you may be able to repair or replace the water main without loosing any time under the DEP investigation process.
If you plumber is not 100% confident and feels that the water leak is coming from another source he will suggest that you wait for DEP and let them perform an investigation on all of the surrounding properties.