A quarter of the homes on one street lost their water lines in 10 days. What makes lines fail together

The cause on that street has not been determined. Houses built by one builder in one season share a lot, though: pipe and fittings from the same orders, the crew and tools that made the joints, the way trenches were bedded and backfilled, and pressure from the same main.

Fittings are a common suspect. Forensic engineers at J.S. Held list installation errors on compression, crimp and expansion joints: missing stiffener inserts in polyethylene tubing, tubing not pushed fully into the fitting, rings off center on the barb, and crimp tools that were never calibrated. Such defects often show up months or years after a system passes its test, they wrote. A crew that made one of those mistakes would have repeated it at every house it plumbed.

Pressure matters too. The International Plumbing Code requires buried water service pipe rated for 160 psi or more at 73.4 F, and a pressure-reducing valve where static pressure in the building exceeds 80 psi, according to a DataDrivenAEC code summary. On Oct. 29, Hard Hat Report covered a new PEX system whose crimps passed an air test and then wept under street pressure above 80 psi.

Who pays depends on local utility rules, and it is often the owner. Denver Water, for example, maintains the mains and leaves service lines to property owners, and the utility says it is not liable for damage those lines cause. Builder warranties generally cover plumbing for two years, according to the Federal Trade Commission, so a 20-year-old line is long out of coverage. Owners should note the pipe material and markings where the line enters the house, read static pressure with a gauge on a hose bib, check whether a pressure-reducing valve is installed, and keep any failed fitting exactly as it came out of the ground, which J.S. Held recommends for any investigation.