Prepare Jars: Examine all jars for cracks or chips and discard any damaged jars. Wash jars and rings in hot soapy water, rinse thoroughly, and keep jars hot in a 180°F oven or simmering water until ready to fill.
Heat Lids: Place new canning lids in a small saucepan, cover with hot water at 180°F, and keep hot until ready to use. Do not boil lids as this may damage the sealing compound.
Ready Canner: Add 2-3 inches of water to your pressure canner and place the rack inside. Begin heating the canner while preparing the soup to save time during processing.
Cook Split Peas: In a large pot, combine rinsed split peas with 6 cups of water or broth. Bring to a boil, reduce heat to medium, and simmer for 30 minutes until peas are tender but not completely mushy.
Prepare Vegetables: In a separate pot, combine diced carrots, celery, and onions with 2-4 cups of water or broth. Bring to a boil and cook for 5 minutes until vegetables are slightly tender but still firm.
Combine Soup: Add the cooked vegetables and their cooking liquid to the split peas, stirring to combine. Add additional hot water or broth as needed to achieve a soup consistency that covers all ingredients well.
Heat for Processing: Bring the combined soup mixture to a boil and maintain heat throughout the filling process. The soup should be very hot when ladled into jars for safe canning temperatures.
Fill Jars: Using a ladle and wide-mouth funnel, fill hot jars with soup, distributing solids evenly among jars. Leave exactly 1 inch headspace from the rim of each jar, adjusting liquid level as needed.
Remove Air and Seal: Add salt and pepper to each jar if desired, then remove air bubbles by running a plastic tool around the inside of each jar. Wipe jar rims thoroughly with a clean, damp cloth and center hot lids on jars with rings finger-tight only.
Process Under Pressure: Place filled jars on the canner rack using a jar lifter, ensuring jars do not touch each other. Lock canner lid in place, heat until steam vents steadily for 10 minutes, then place pressure regulator on vent and process at 11 pounds pressure for 100 minutes for quarts or 75 minutes for pints. Adjust pressure for altitude: 1,001-2,000 feet use 11 lbs, 2,001-4,000 feet use 12 lbs, 4,001-6,000 feet use 13 lbs, 6,001-8,000 feet use 14 lbs. After processing, turn off heat and let pressure return to zero naturally before opening canner.
