Leaky pipes and water mains

Oct 2, 2008 by

The case of the month involves the investigation of leaking inch, inch and a half, and two inch copper water mains and lateral lines in a community servicing approximately a thousand homes.   Beginning in April of the first year, a contractor replaced all the mains and laterals.   By May of the following year, water leaks developed at various angle meter stops, sometimes even breaking through the surface of the asphalt streets.   When we were assigned to examine the records and installation of the water system, including the joints used, and determine the cause of the leaks, the number of reported leaking connections was more than 200.    That is a lot of lost water for a city with a new water system.

Our initial efforts in this case involved attempting to get access to the sites, getting a report of the full extent of the leaks found, and to physically examine the flared connections which had been removed.     We contacted the general contractor who provided a complete copy of their project files.   In those files, we discovered a meeting had already occurred in November between the city, the water district (WD), the general contractor, the plumbing subcontractor, and the manufacturer of the copper pipe.

The parties had taken samples of the pipe removed from a few of the leaking sites and had determined that the copper pipe was often harder than the specified maximum hardness for the pipe allowed by the contract specifications.     In other words, the contractors blamed the manufacturer’s hard pipes for the leaks.     However, our expert was unable to draw that conclusion that the hardness of the pipe necessarily would result in leaking flared connections.    The metallurgical reports on the hardness of the pipe did not show or comment upon a causal relationship to the waterline leaks.

Eventually, we performed our first site examination.    When we arrived at the location, it was obvious that there was a water leak underneath the street coming from the connection to the corporate stop at that location. We observed the WD excavation and examination of the leak.    The leak, indeed, was quite sizeable and after the WD removed the pipe connection and repaired the lateral pipe, the flared connection, and in particular the flare itself, was examined.    Our expert measured the wall thickness of the pipe itself, which varied from .058 to .064, and also the thickness of the flare, which varied from .052 to .068.    In particular, the thickest spot of the flare (.068) was between the two fluid cut sections of the flare.     Since this was thicker than the original parent material, it was obvious that additional material was present to form the thick spot on the flare; i.e. a burr from the cutoff operation for the pipe at that section had not been completely removed as required by good workmanship.    The pipe itself was identified as being manufactured by the same company.

Subsequently, we went to another reported leak site.    This leak was at the angle meter stop.    The WD removed and replaced the angle meter stop and joint connection.   We noticed the joint in question had an excess of pipe dope around the flared connection, indicating that a leak had been noticed at this stop and pipe dope was added in an effort to stop the leak.    We also observed the flared connection was smaller than normal and when compared to an exemplar, found that the maximum diameter of the flare was indeed less than it should have been in making a properly formed flare.   This again indicated good workmanship was lacking in that the flare was not expanded to the full diameter required to make a good joint.

The water district provided us with samples of the pipe being used for the repairs, which we used for further examination and evaluation.    The ends of the pipe were cut off by the WD personnel with a tube cutter, leaving  burrs on the inside diameters.    We removed the burrs with a burring knife, and used a newly purchased impact flaring tool to form a flare at the end. The flare formed according to specifications and took 10 strong hammer blows to the flaring tool to fully form it.

We cut another section of the tubing with a tube cutter, which again left an internal burr at the end of the pipe.    We then flared that end with the flaring tool without removing the interior burr.    This operation left a castellated edge around the perimeter of the flare, which would be a defect, and which would lead to a leak (such as we observed in the first inspection).    We formed a second flare on a deburred edge and this did not have such a castellated edge.    A third flaring operation was performed after deburring only a portion of the interior perimeter of the pipe.    This third flare was flared using the same procedures as before, and the typical castellated lip of the flare resulted in that portion which was not deburred.

A review of various standards emphasized the extreme importance of deburring the ends of the pipe to prevent a leak from forming.    For example, the standard “IAPMO IS3-87” which describes how to flare joints using an impact flaring tool, specifies in paragraph 802.1 “remove all burrs.   This is very important to assure metal-to-metal contact.”     Other references reviewed also repeated the admonition that it is extremely important for burrs to be removed from the pipe before the flaring operation is performed.

Based upon the information revealed by the excavation of two locations, and many other test samples, we concluded  many flares were formed without the benefit of proper de-burring of the cut edge of the pipe prior to flaring.    Examination of other flared connections revealed the flares were not flared to the full required diameter and should have been made larger.

Our final conclusion: it was not the hardness of the copper that caused the leaks.    The cause of the leaks in the project was poor workmanship by the plumbing subcontractor.