Inspecting plumbing in residential homes has become more complicated with the proliferation of Pex type plumbing lines. What is PEX? The PE in PEX refers to polyethylene, the raw material used to make PEX. The X refers to the crosslinking of the polyethylene across its molecular chains. Currently, three methods exist to crosslink PEX. However, all three methods of manufacturing PEX are subject to the same ASTM standards for use in domestic water systems.
Not all Pex Plumbing lines are created equal. Below are the Material Designation Codes that manufactures use to identify ratings of tests.
Material designation codes
Material designation codes are four-digit, numerical codes that are located after the brand name on the print stream (i.e., PEX XXXX). The codes are tested in accordance with and defined by ASTM F876. Each digit in the code is further explained below.
The first digit in the material designation code is for chlorine resistance tested in accordance with ASTM F2023. A digit 5 indicates the PEX piping has been tested and meets the requirements for minimum chlorine resistance at end-use conditions 100 percent of the time at 140°F (60°C). A digit 5 is the highest classification for chlorine resistance. A digit 3 indicates end-use condition of 50 percent at 140°F and 50 percent at 73°F. A digit 1 indicates an end use condition of 25 percent at 140°F (60°C) and 75 percent at 73°F (23°C). A digit of 0 indicates the pipe has not been tested or rated.
The second digit is for demonstrated ultraviolet (UV) resistance of PEX material when tested in accordance with ASTM F2657. A digit of 1 indicates the PEX piping has a UV resistance of 30 days. A digit of 2 means the pipe has a UV resistance of 90 days. A digit of 3 indicates a UV resistance of 180 days.A digit of 0 means the pipe has not been tested or rated.
The third and fourth digits are for hydrostatic design stress (HDS) as tested in accordance with the Plastics Pipe Institute (PPI) Technical Report TR-4. A digit of 06 indicates the PEX piping has an HDS of 73°F (23°C) at 630 psi. A digit of 08 indicates the PEX piping has an HDS of 73°F (23°C) at 800 psi.
WHAT IS POLYBUTYLENE PIPE? Polybutylene is a plastic water supply piping that hit the market in the mid to late 1970’s and was used in the residential marketplace all the way through the mid 1990’s. Typically it is gray in color and it was marketed as the “pipe of the future.”
Some of the problems associated with Polybutylene pipe were that Aluminum Crimp Rings which was blamed for many failures of the polybutylene piping. When crimp rings were switched to copper there were still failures occurring and most of the blame was then directed at the plastic itself. New installation methods included a manifold that eliminated any connections other than at manifold and fixture. Eventually polybutylene was replaced in the marketplace with PEX.
The main problem with polybutylene is that it deteriorates faster than other types of approved plumbing materials. Chlorine in the water is suspected as being the main cause of failure as some areas have higher failure rates than others.
RECOMMENDATIONS AND LIMITATIONS TO PB USAGE:
- Do not use plastic piping in a continuously circulating hot water plumbing loop.
- Do not use where water temperatures could exceed 180 degrees F.
- Do not use in an application where the plastic pipe will be exposed to direct sunlight.
- Do not allow pipe to be left exposed to direct sunlight for more than 30 days during or before construction.
- Do not use acetal (plastic) fittings.
- Water heater connections should be made with metal (copper) connectors at least 18″ long.
- Pipe must be kept at least 6 inches from hot water tank or furnace flue pipes.
- Polybutylene piping is not suitable for swimming pool piping systems, or where more than 2ppm of chlorine (free residual) will be routinely encountered.
The Barrie Home Inspector is continually upgrading knowledge and training to provide the best possible service to his clients.