Leak Sealer F4 is a internal leak sealer developed for use throughout a central heating system to seal small, inaccessible leaks and weeps which may cause pressure loss and boiler breakdown. Once dispersed within the system, the product finds the area of oxygen ingress and forms a polymer to seal the pinhole. Effective within 1-24 hours after application, the unique sealing efficiency of this market-leading water treatment chemical has been proven to prevent blockages or restrictions within the boiler or vulnerable system components such as pumps and safety devices. A leak can be quickly and efficiently sealed, without the need for a complete system drain down. The Fernox Express range uses Barrier Pressure Pack technology and compressed air propellent to expel the product so the entire range is non-flammable. The propellent (compressed air) is not mixed with the active product so there is no risk of air ingress into the system which could accelerate future risk of corrosion.

Seeks out and seals inaccessible, internal microscopic leaks fast

Quick and convenient – doses in 30 seconds – no need to drain down the system

Safe to use – does not cause blockages in pipework or vulnerable boiler components such as pumps, air vents and heat exchangers

Non-toxic, environmentally friendly formulation, compressed air propellant and 100% recyclable can

Saves time and money on draining down and repairing.

Add via a radiator, filling loop or TF1 System Filter – all adapters supplied