Fernox Leak Sealer F4 is an internal leak sealer developed for central heating systems to seal small, inaccessible leaks and weeping joints that cause pressure loss. Once dispersed, it locates areas of oxygen ingress to form a durable polymer seal without causing blockages in boilers, pumps, or safety devices.
Effective within 1 to 24 hours of application, this formula eliminates the need for complete system drain downs. A single 500ml dose treats up to 130 litres of system water, making it fully compatible with all metals including aluminium as well as underfloor heating systems.
Brand
Fernox
Product Type
Central Heating Leak Sealer
Volume
500 ml
Length
182 mm
Width
88 mm
Height
52 mm
Weight
0.6 kg
System Coverage
Up to 130 L (16 radiators / 250 m² underfloor)
Curing Time
1 to 24 hours
Material Compatibility
All metals including aluminium, plastics, and synthetic materials