Limescale build-up inside household appliances can cause them to run less effectively, increases the likelihood of premature breakdown and impairs the efficiency of heat transfer. The Sentinel SESI is a cost-effective scale inhibitor solution to help tackle limescale build up and could save up to £130 a year on typical energy bills.Sentinel SESI is an electrolytic scale inhibitor, a cost-effective solution to help tackle limescale build up. It provides a long term solution which requires no maintenance and protects the whole house without introducing any undesirable chemicals to drinking water. Sentinel SESI is easy to fit, WRAS-approved and comes with a 5 year guarantee. Compare prices from: Sentinel in Plumbing