- The ProPEX® Engineered Polymer (EP) Reducing Tee makes diverting connections for Uponor cross linked polyethylene (PEX-a) tubing for use in hot and cold domestic potable water systems, residential fire sprinkler systems and hydronic radiant heating and cooling systems. Each end of the tee is manufactured with an Uponor ProPEX® fitting for connections to Uponor AquaPEX® or Wirsbo hePEX™ tubing.