The Neo-Pure High Efficiency Replacement Control Valve is the replacement control valve for the Neo-Pure High Efficiency Upflow Water Softeners. When hard water minerals are combined with heat it forms scale build-up. Scale causes costly build-up in your plumbing, water heater and other water-using appliances. When combined with soap, the minerals form soap curd or scum that makes skin dry and itchy, hair lifeless, laundry dull, and builds up on fixtures.