Place raspberries in a large pot with the water. Crush lightly with a potato masher. Bring to a simmer over medium heat and cook for 5 to 8 minutes until berries have completely broken down. Pour into a damp jelly bag or cheesecloth-lined strainer over a bowl. Let drip for at least 4 hours or overnight.

Measure 5 cups of strained juice into a large, deep pot. Add 5 cups of sugar (1 cup sugar per cup of juice). Bring to a boil over medium-high heat, stirring frequently. Continue boiling until the mixture reaches 220°F, about 30 minutes. Stir often to prevent scorching and watch for boil-overs.

Remove from heat and skim off foam. Ladle hot jelly into prepared jars, leaving 1/4 inch headspace. Wipe rims, apply lids and bands to fingertip tight.

Lower filled jars into a prepared water bath canner. Process for 10 minutes for half pints or pints, adjusting for altitude.

Turn off heat and let jars stand in canner for 5 minutes. Remove to a towel-lined counter and cool undisturbed for 12 to 24 hours. Check seals before storing.