Leak Sealer F4 is suitable to be used throughout a central heating system to seal small leaks and weeps which may cause pressure loss and boiler breakdown. Once dispersed within the system it will be effective 1-24 hours after application. The unique sealing efficiency of this proven product has been specifically developed to prevent blockages or restrictions within the boiler or vulnerable system components such as pumps and safety devices.

  • Ideal for reducing pressure loss from sealed systems
  • Seals most weeps and small inaccessible leaks
  • Saves time and money on draining down and repairing
  • Does not cause blockages of pump, air vents etc
  • Compatible with all metals and materials commonly used in central heating systems

Application and Dosage

Use 500ml Fernox Leak Sealer F4 for every 100 litres of circulating water (approximately 10 single radiators) 1. Almost empty the central heating header tank, and then pour in the Leak Sealer F4. 2. Draw off 5-10 litres of water from the drain cock and return this to the header tank to ensure that no Leak Sealer F4 treated water is thrown away. 3. Repeat step 2 until all Leak Sealer F4 has been drawn into the circulating system. DO NOT simply leave the Leak Sealer F4 in the header tank. 4. Switch on the circulating pump and apply at least a small amount of heat to achieve an even distribution. In single feed indirect cylinders, e.g. ‘Primatic’ or similar, potable water chemicals must be used.

Physical Properties

Fernox Leak Sealer F4 is a Polymer Emulsion.
Colour: Off white
Odour: Faint Form: Liquid
pH (conc.): 5.0 – 7.0
pH (soln): 7.85
SG: 1.0 at 20°C

Packaging, Handling and Storage

Leak Sealer F4 is supplied in 500 ml containers. Fernox Leak Sealer F4 is classified as non-hazardous, but as with all chemicals keep out of reach of children. In case of contact with skin or eyes, rinse immediately with plenty of water. Fernox Leak Sealer F4 is compatible with all Fernox products.

Please contact the supplier to check availability of stock