Fast Internal Leak Repair for Heating Systems
Fernox Leak Sealer Express provides a quick and effective way to seal small internal leaks in central heating systems. It targets hard-to-reach areas, including micro leaks within pipework, radiators, and heat exchangers.
Small leaks often cause pressure loss and frequent boiler lockouts. Therefore, rapid intervention is essential. Fernox Leak Sealer Express helps restore system pressure and stability without major disruption.
Thanks to its aerosol format, installers can treat systems quickly during service visits.
What Is Fernox Leak Sealer Express?
Fernox Leak Sealer Express is a concentrated internal leak repair chemical supplied in a convenient 400ml aerosol. It circulates with system water to locate and seal leaks from the inside.
Users inject the product directly into a radiator, filling loop, or dosing point. As a result, there is no need to drain the system or remove components.
Fernox designed this product for sealed heating systems operating under pressure.
How Fernox Leak Sealer Express Works
Once inside the system, Fernox Leak Sealer Express circulates with the heating water. It detects pressure drops caused by leaks and reacts at those points.
The formula forms a durable seal when it contacts air at the leak site. Consequently, it closes micro leaks without blocking pumps, valves, or heat exchangers.
The seal remains stable under normal operating temperatures and pressures, ensuring reliable system performance.
Key Benefits of Fernox F4 Express
Seals small internal leaks quickly
Eliminates the need to drain the system
Aerosol format allows fast, clean dosing
Targets inaccessible leaks effectively
Compatible with common system materials
Ideal for emergency and preventative repairs
Because of these benefits, heating engineers trust Fernox F4 Express for rapid fault resolution.
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.
Next Working Day Delivery: Yes, we hold all our products in stock at our 7000 sq ft Nottingham warehouse and at our 3000 sq ft warehouse in Market Harborough and use DPD for a tracked next-day delivery.
Collection Available: You can always collect from our Nottingham location and help yourself to a free tea and coffee.









