Combine the raspberries and rhubarb with the water in a heavy saucepan. Cook over medium heat for an hour or until the rhubarb is tender. Dump in the pectin, stirring constantly. Bring mixture to a full rolling boil, stirring constantly. Boil for 4 minutes, skimming the foam.
Ladle the hot mixture into hot sterilized jars leaving a half-inch headspace. Seal with not 2-piece lids. Process in a hot water bath for 10 minutes.
Yield: 3 to 4 pints