1. Drain clams and reserve liquid. Measure clam liquid; add enough water to make 4 cups liquid and set aside. 2. In the pressure cooker, brown diced Bacon until golden. Remove Bacon and set aside. 3. Drain off all but 1/4 of the fat and saute Onion for several minutes. 4. Add potatoes, salt, pepper and reserved clam liquid (mixed with water) and bring to a boil. 5. Seal, bring up to 15 lb. pressure, reduce heat to stabilize pressure and cook for 10 minutes. 6. Remove from heat, depressurize and remove lid.