Assemble the Expansion Tank Connections
Make sure that the length of the pipe coming off the 'T' is as short as possible to limit strain on the connection.
Clean and flux the joints while assembling the expansion tank connection. Make sure there is a threaded male adaptor to connect the tank into at the end.
Solder all the joints together and let the assembly cool thoroughly, then add Teflon paste to the threads of the tank.
Install the 'T' and female adaptor for the expansion tank. Use two slip-joint pliers to screw the tank into the threaded male adaptor (Image). Be sure the tank is secure.
If the water heater is electric, turn the water on and test for leaks.