What Causes a Water Main Break?

April 15, 2020

What Causes a Water Main Break?

Thousands of property owners across NYC experience water main breaks on an annual basis. Most property owners will repair the leak without understanding the actual cause of the leak. In some cases, it may be a challenge to determine the complete reason behind the leak, but it’s important to understand all of the possible variables. Here are some variables that may help determine what may cause a water main break:

  1. Wear and tear are common causes of a water main break— especially if the material of your existing water main is made up of lead or galvanized pipe. If you currently have a lead or galvanized main, it’s most likely more than sixty years old, this age is susceptible to breaking as a result of natural wear and tear.  The average life span for a water main in NYC is around sixty years.
  2. Damage caused by another contractor is another reason why your water main may break. In NYC, most of our utilities are located below ground. If another contractor working on gas, electric, cable etc. must install any new piping, there is a good chance they are required to dig near your water main to complete the repair. Other utility repairs may cause damage to your water main if your contractor is unaware or not careful of their work.

Recently a water main repair in Brooklyn was completed after the homeowner received a 3-day notice violation from the city due to their water main leak. As it turned out, the gas company was digging in the exact area of their water main in the roadway one day prior and suddenly, the water main started to leak. Is this a coincidence? Probably not.

  1. Water main leaks from electrolysis have become more common over time. Damage to a water main caused by electrolysis is a result of an underground DC current leak that creates small holes and green stains on copper water mains. These small holes are referred to as pitting, which commonly causes leaks on new copper water mains as well as old. When installing a new water main, it’s always suggested to install the copper inside of a plastic sleeve which has been proven to prevent electrolysis.

Historically, the stray current was thought to only have come from underground electric cables, but recently there have been reports stating that the new fiber optic cable lines have begun to cause water main leaks due to electrolysis.

In 2017-2018, there were over one hundred water main leaks reported on 188 St. in Queens that were determined to have been a result of electrolysis. Allegedly, the cable company who was responsible for the fiber optic cables ended up reimbursing the property owners for their water main replacements.

Copper water main installation

  1. A faulty or illegal water main repair is far too common and is usually a result of a non-licensed plumber performing work, or a licensed plumber attempting to cut cost by taking a shortcut. This means that the plumber may have used two different alloys of metal and completed a partial repair on the water main when a full line replacement was required. It’s common to have a water main leak when connecting two dissimilar metals as part of the repair.


There may also be cases where un unqualified plumber tries to save a few dollars by reconnecting the new water main to an old fitting. In the plumbing industry this is viewed as subpar work and is largely frowned upon.

Recently, a Brooklyn-based water main repair was needed after it was discovered that the previous plumber installed a clamp over the existing leaking pipe—creating a partial fix instead of a complete repair. Not only was the clamp viewed to be shoddy plumbing, but it is also illegal to install a water main clamp on a lead water main in NYC. A water main clamp installed below ground is guaranteed to fail as time goes on. The water main should have been replaced in its entirety with a new copper pipe

  1. Damage caused by a new tree planted on the city sidewalk is not as common as the other reasons behind water main breaks, but it does occur—commonly in the summer months. In this case, the water main leak may not surface for a few days as there may only be a small crack in the pipe. A small leak will take time to find its way to the surface after the tree was planted with compacted soil.


If you have any questions specific to your water main leak and the possible cause, speak with a NYC licensed and bonded plumber to assist with your assessment and come up with the best solution for your repair.

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