Locate the area where the arbor will be built. Dig four holes 10" deep for corner posts. The holes should form a rectangle that is 5' by 3'. Place a 12" PVC pipe segment in each hole. Secure it in place by packing the hole with dirt or cement.
Place a T connector on top of each 12" PVC pipe segment. Connect each side of the arbor with a 3' segment of PVC pipe between the T connectors.
Place a 12" segment of PVC pipe in the remaining opening of each T connector. Place a T connector on top of the pipe segment. Repeat until there are 7 12" segments of pipe on each pole (8, including the one in the ground). Top the last pipe segment with a 3-way corner connector.
Place a 6" segment of PVC pipe in the 3-way corner connector opening. Place a T connector on the end. Repeat until both sides of the arbor have been connected together.
Connect all the middle openings of the connectors with a 3' section of PVC pipe.