PEX tubing is approved for direct burial outdoors. Direct burial is most often necessary when running the water supply line to a house. Although PEX resists freezing well, it can burst if water were to freeze in the line. It’s a must, therefore, to bury the tubing below the frost line. (Depth of the frost line in a given area can be obtained by contacting the town or local water company). Dezincification-resistant brass PEX fittings or plastic PEX fittings should be used in areas known to have aggressive soil.
Residential water supply lines generally use 3/4” pipe (occasionally 1”). SupplyHouse carries PEX-B tubing in these sizes, as well as PEX-A rated AquaPEX. Sleeving the buried PEX (in PVC, for example) can make potential repairs easier, and embedding PEX in sand protects it from any rocks in the soil. Always check with all local and municipal codes prior to installation.
