In a medium saucepan combine the water and ginger. Bring to boiling; reduce heat. Simmer, covered, for 5 minutes. Remove from heat; stir in tea. Cover and let stand for 5 minutes. Pour mixture through a fine-mesh sieve into a large liquid measuring cup; discard solids. Measure exactly 3 1/2 cups liquid, adding water or discarding liquid if necessary.
Transfer the 3 1/2 cups liquid to a 6- to 8-quart heavy pot. Stir in pectin and lemon juice. Bring mixture to a full rolling boil, stirring constantly. Stir in sugar. Return to a full rolling boil, stirring constantly. Boil hard for 1 minute, stirring constantly. Remove from heat. Quickly skim off foam with a metal spoon.
Ladle hot jelly into hot sterilized half-pint canning jars, leaving a 1/4-inch headspace. Wipe jar rims; adjust lids and screw bands.
Process filled jars in a boiling-water canner for 10 minutes (start timing when water returns to boiling). Remove jars from canner; cool on wire racks. Makes 6 half-pints.