The PureT 4UT44 union tee is used when you need to split one water line into two outlets or combine two lines into one, commonly seen in dual-filtration setups, bypass loops, or when adding a pressure gauge or flush valve to an existing RO system line. All three ports accept standard 1/4" OD tubing used in most residential reverse osmosis and under-sink filtration systems. Push the tubing firmly into each port until it stops; the internal collet grips the tube securely without tools or thread sealant.