This PVC80U4 4" Schedule 80 PVC union is used to install a PVC DWV pipe system beneath a kitchen sink or bathroom to help prevent sewer gas from entering the building. It also connects two pipes but is quite different from a coupling, as it allows future disconnection of the pipes for maintenance. A union allows easy connection and disconnection, multiple times if needed, which can be detached without causing any deformation to the pipes. The union joint is self-sealing and no Teflon tape is required. With its functionality, this fitting is widely demanded in the pipe fitting market. Here at PlumbersStock, we carry a wide range of fittings for your plumbing needs. And we offer these products for you to own at a very reasonable price.