Anti-freeze valves and glycol are two different components that serve similar purposes in a heat pump system. Glycol is a type of anti-freeze that is commonly used in heat pump systems to prevent the water in the system from freezing in cold weather. Glycol is specifically designed to lower the freezing point of water, which is necessary to prevent damage to the system in cold conditions. Anti-freeze valves, on the other hand, are designed to automatically open and drain out the water within the system when the water drops below a certain temperature.