About SESI

Limescale prevention for domestic properties

Sentinel SESI is an electrolytic scale inhibitor for domestic hot water systems. SESI is a cost-effective and low-maintenance way to protect a property against the damaging and expensive impact of limescale.


Sentinel's electrolytic technology has been independently verified as best in class. Our devices distribute more scale-controlling zinc than other popular electrolytic devices available on the market.

Comparative effectiveness against other leading brands:

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Technology overview

  Electrolytic Magnetic Polyphosphate Water softeners
Recommended by the UK Building Regulations Compliance Guide
Suitable for a whole house
No regular replenishing/maintenance required
No undesirable chemicals added to water
Non-corrosive to system metals

Installation and Maintenance

Installation of a SESI is made quick and easy:

  • 15mm compression fittings and a double hex
  • can be installed onto pipework of any orientation, making siting of the device as easy as can be

The device can be installed on the incoming water main to protect the entire property against the damaging and expensive effects of limescale: including the boiler, pipework, and appliances which heat water such as the washing machine or dishwasher.

This product requires no maintenance following install and will protect the property for approximately ten years, based on average domestic household water usage.

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Protect heating and hot water with Sentinel SystemCare Hard Water

To ensure your boiler stock and their manufacturer warranties are fully protected, it makes sense to commission the heating and hot water systems to UK Building Regulation Part L requirements, by using quality water treatment and scale protection products.

SystemCare blends market-leading products with services such as training and independent laboratory analyses to ensure that upon installation, every boiler receives the required type and level of water treatment to optimise system performance. Our aim is to make the treatment process easy for customers.