King County Jail, Seattle
Tests showed copper-pipe failures were caused by aggressive water, high water velocity and potential installation issues. The county selected polypropylene pipe for the water-pipe replacement because it is durable, chemically inert and corrosion-proof. The heat-fusion process used to connect the pipe and fittings involves no flames; the pipe and desired fitting are simply inserted into a welding device and heated for a specified time before being joined together.
New 6- and 8-inch Green Pipe cold water mains and 4-inch hot-water mains with 3-inch risers were run to all water closets; 11/2 – to 3/4 -inch branches for supply lines were run to individual cells. Green Pipe SDR 7.4 (faser) was used for the hot water and SDR 11 (non-faser) was used for the cold water. The faser pipe contains an extruded core layer of fiberglass that increases the rigidity and working pressure of the pipe at hot-water temperatures. SDR (standard dimension ratio) is the ratio of pipe diameter to wall thickness, and the SDR 7.4 faser pipe is high-heat stabilized, allowing it to handle temperatures up to 200 F at 30 psi.
Polypropylene pipe manufacturer: Aquatherm
Built in the mid-1980s, the King County Jail houses more than 1,000 inmates and employs approximately 350 correctional staff. After about 11 years in operation, the domestic water piping system began to leak. Copper had been used for the building’s distribution system with 4-inch and 6-inch galvanized steel mains distributing water in the sixth-floor mechanical rooms.
The county signed off on a renovation project that included $3.6 million just for re-piping. In addition to utilizing new pipe material, county staff and Wood Harbinger redesigned the hot-water recirculating systems to control the velocity and flow rate.
The job required the majority of water lines to remain active. The installers had to be within sight of a jail officer escort during the re-pipe work, which took place between 7 p.m. and 6:30 a.m.