1. Fernox 56703 F4 Superconcentrate Central Heating Leak Sealer

    Model: 56703
    Availability: same day dispatch Same day dispatch if ordered before 1:00 pm
    Price:   £21.50

Fernox Superconcentrate Leak Sealer F4 is used throughout domestic heating systems for sealing small inaccessible leaks. Leak Sealer F4 works best in warm/hot circulating water and once evenly dispersed will usually be effective within 1 - 24 hours.

The sealing efficiency of Leak Sealer F4 has been intentionally limited to prevent blockage of safety devices, pumps, etc. For long term protection against corrosion and limescale it is recommended systems are cleansed using an appropriate Fernox Restorer and then protected with a Fernox Protector 



  • Easily and quickly added via one of the radiators
  • Universal applicator included 
  • Patented application
  • Ideal for pressurised systems and combination boilers
  • Non-toxic, environmentally friendly