Pour water into a pressure cooker. Add split peas, ham hock, onion, celery, thyme, garlic powder, and black pepper. Close cooker securely and place pressure regulator over vent according to manufacturer's instructions. Bring to high pressure; adjust temperature until regulator is gently rocking. Cook, about 30 minutes.

Pour cold water over the pressure cooker to release pressure according to manufacturer's instructions.

Remove ham hock and strip off meat; add to soup. Stir well to distribute flavors. Season with salt and hot pepper sauce.