Directions:Sterilize and dry enough mason jars to store five pints of marmalade, and set aside. Wash the pomelos, cut them in half and squeeze out the juice. Place the pith and pips (the white part of the fruit) into a muslin bag. Shred the peel and soak it in the water overnight, along with the muslin bag. Place the peel, muslin bag, and water into a pressure cooker and bring it up to 15 pounds of pressure. Cook for about 15 minutes. Reduce the pressure once the water reaches room temperature. Test the peel for tenderness by pinching a cooled piece between your thumb and forefinger. If the peel is soft, remove the muslin bag from the water and wring it out into the cooker. Then add the sugar. Stir over gentle heat until the sugar is dissolved, then boil it rapidly in the open cooker until it reaches 221° F. Skim away any foam that forms, and allow the marmalade to cool until a skin starts to form. Pour it into warm, dry jars. Cover each jar with a waxed disc until cool, then replace the discs with permanent lids.