The multiple tank system assures you have soft water 24 hours ever day, even during the regeneration process. One tank is always in service while the other tank is either on standby or regenerating. This system is ideal for households with larger families, multiple bathrooms and showers that are used often every day. The Twin is recommended where treated water needs to be delivered at all times of the day. The Alternating Twin is known as the Cadillac of water softeners.