Heat water in a large stockpot. Add pork meat, spare ribs, onion, and garlic. Bring to a boil, then lower the heat and let simmer, partially covered for 2 and half hours or until meat is tender and falling off the bone. Season with salt when meat is almost done. While cooking, skim the top layer of foam and fat from the pot using a ladle. If necessary, add warm water to maintain the same level of broth in the pot.