Pour the water in the slow cooker, followed by the onion, carrots and potatoes.
Rub the salt and pepper over the roast, then put on top of the vegetables.
Sprinkle the Worcestershire sauce, garlic powder and onion soup mix evenly over the contents of the slow cooker.
Cook on low for 4 hours or until the meat is to the correct temperature using a meat thermometer - (145°F for medium rare; 160°F for medium). Turn off the slow cooker when 5 degrees away from desired temperature - roast will continue cooking after turning off slow cooker.