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Re-piping a Gas System

I’m on the board of a 10-story, 47-unit cooperative in Brooklyn, and a resident recently detected a gas leak in her apartment. After our superintendent couldn’t find the cause of the leak, we called a plumber, who couldn’t isolate it either. KeySpan has since shut off our system, leaving us without gas for heating and cooking. They said they could not reinstate service until the leak was fixed. The gas piping in our building is nearly 80 years old. Will we require a whole new system, or can we just replace the faulty sections? How long should we expect it to take before our gas is up and running again?

While it’s certainly an inconvenience to be without heat and the means to cook, leaking gas is an obvious safety hazard that can’t be dismissed, which is why the utility is required by law to shut down your service until the leak is fixed. In some systems, the heating gas and the cooking gas are on separate lines, so if the leak can be traced to one line or the other, then only the line with the leak will need to be turned off. Gas-fired chillers and oil-burning heating systems that have gas-lit pilot lights are also affected during a gas-system shut down, as well as gas-fired clothes dryers.

Now that your system is down, you will need to go through a series of steps to get your gas service up and running again. First off, after a gas leak is detected and the gas is turned off, the plumber will try to isolate the origin of the leak by pressure-testing the major components of the system: mains, risers, branch lines, and valves. Gas mains bring the gas from the utility line to common risers, which transport the gas to the different floors, where they connect to branch lines, which bring it to individual apartments. (In some systems, individual risers connect the main line to the apartments.) Valves, located at the base of risers and/or at branch lines, allow for the flow of the gas to be turned on and off.

The plumber will go through the entire system, testing the lines to determine which lines “hold” adequate pressure and which ones don’t. If the leak is limited to just one or two areas, then usually only those sections of piping will need replacement. But if leaks are found throughout the system, especially in an older building such as yours, it’s usually a sign that it’s time to undertake a re-piping of the entire system.

If your plumber determines that the extent of the leaks is extensive enough to warrant replacement of all the gas piping, the first step will be to determine where the new gas lines are to be run. It’s recommended that the board consult with a professional engineer to ensure that the locations of the new pipes are safe, feasible, and code-compliant. In most cases, to avoid demolition and to intrude on residents as little as possible, the existing risers (especially those running behind walls) are abandoned and left in place.

Depending on the building’s design and aesthetic considerations, some boards may decide to run the new lines exposed in individual apartments. The New York City Building Code prohibits gas piping in public hallways and stairwells unless placed in a fire-rated enclosure that does not block fire egress. Gas piping also cannot be run in a ventilation shaft; however, a legally abandoned dumbwaiter or elevator shaft would be permissible. Installing piping outside the building is also permitted but tends to be prohibitively expensive.

Once the location of the new piping has been determined, the lines are installed, usually starting with the large mains and risers, followed by the branch lines to individual apartments. Each length of new piping is pressure-tested as it is installed to avoid the complications of trying to detect leaks only after the entire system is rebuilt. The pressure tests are typically performed to meet a standard higher than that set by the New York City Department of Buildings (DOB), so it will pass inspection when the final test is conducted after the re-piping is complete.

The new system should be designed with isolation valves, which allow the gas to be shut off to dedicated lines while leaving others intact. These valves will avoid the need to shut down the entire system if leaks arise in the future. Older systems, such as the one in your building, usually do not have isolation valves but instead have only one main valve from the utility. In this set-up, when there’s a leak in any section the entire system has to be shut down. Any new piping behind walls or enclosures must have doors to allow access to valves. Finally, a booster pump may be required if your building needs high-pressure gas but only low-pressure gas is available from the utility.

A set of design drawings detailing the layout of the piping and associated components needs to be maintained by the engineer and/or plumber. These drawings are filed with the DOB before the project begins, along with application forms that provide a description of what will be demolished, removed, and installed. In some instances, after the project is completed, an amended set of drawings (i.e., “as-built” plans) and forms may be resubmitted to the DOB with revisions to reflect any changes that took place during the course of the project. (For landmark district properties, approval must also be obtained from the Landmarks Preservation Commission.)

Once the new gas piping is fully installed, the plumber must conduct a pressure test (typically three pounds per square inch) under DOB inspection before the utility can reinstate gas service. The DOB inspector will also evaluate the condition of old piping (if any remains), how the new piping is installed, and whether everything complies with code, such as proper fireproofing where required. To enable the inspector to thoroughly check the system, new pipes cannot be concealed or painted until after the inspection.

Unfortunately, it can take up to six months from the time a gas leak is detected until new piping is put in place, the system passes DOB inspection, and the utility can turn gas service back on. During this interval, buildings with dual-fuel systems can operate on oil for heating. (For buildings with oil-fired systems, the board may want to consider converting to an interruptible-gas system as part of the re-piping project.)

One word of caution: once the new system is up and running again, the board should be mindful when approving a resident’s renovations to an apartment. Gas lines can be easily damaged when removing a wall, floor, ceiling, or enclosure, so they should be treated with the same caution during demolition as a live electrical wire.

Rand Engineering P.C. has been providing integrated engineering and architectural services to the co-op and condo community since 1987.

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