Fernox Leak Sealer F4 is an internal leak sealer designed for use in central heating systems to seal small, inaccessible leaks and weeps that can cause pressure loss and boiler breakdowns.
Once added to the heating system, F4 circulates through the system and seeks out areas where oxygen is entering through microscopic leaks. It then forms a polymer seal around the affected area, helping to stop the leak without the need to drain down the entire system.
Fernox F4 is effective within 1 to 24 hours and is designed to remain permanently in the system. It is compatible with all common heating system metals and materials, including aluminium, and is formulated not to cause blockages or restrictions in vulnerable components such as pumps, air vents and heat exchangers.
One 500ml bottle treats up to 130 litres of system water, equivalent to up to 16 radiators or 250m² of underfloor heating.
Fernox LS-X is a fast-acting silicone paste designed to seal external leaks and joints on hot and cold water services. It is particularly useful for repairing leaks around compression joints and screwed fittings without the need for mixing or specialist preparation.
The ready-to-use paste remains flexible rather than setting rock hard, allowing joints to be dismantled when required. It does not shrink or crack with age and can be used across a wide temperature range, from below freezing to above the boiling point of water.
LS-X can also be used as a jointing compound on hot and cold water services, including potable water. For larger leaks or higher pressures, Fernox recommends reinforcing the repair with PTFE or another suitable reinforcement tape.