Leak Sealer F4 Express 400ml

Product Code: 62438 Category:

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
  • One single dose of this product treats a larger sized property with a heating system of 130 litres, up to 16 radiators or 250 sqm of underfloor heating and is added via a radiator or filling loop. Fernox Leak Sealer F4 Express can be dispensed directly into a radiator air vent or system filling loop using the appropriate special adapter supplied with the product. The whole process takes less than two minutes.

    In single feed indirect cylinder, e.g. 'Primatic' or similar, potable water chemicals must be used.


    Fernox Leak Sealer F4 Express is supplied in 400 ml aerosol cans with a universal applicator set.

    Fernox Leak Sealer F4 Express is classified as non-hazardous, but as with all chemicals: Keep out of reach of children. Do not mix with other chemicals. Do not take internally. In case of contact with eyes or skin, rinse immediately with plenty of water.


    Colour: White
    Form: Viscous liquid
    Odour: Faint
    PH: 5.0 – 7.0
    SG: 1.0 @ 20°C

    Single Item

    Height (mm)Width (mm)Depth (mm)Weight (kg)EAN Barcode
    218
    66
    95
    0.53
    5.01455E+12

    Outer Carton

    Height (mm)Width (mm)Depth (mm)Weight (kg)ITF Barcode
    241
    178
    339
    5.56
    5.01455E+13

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