Seal leaks fast with Fernox Leak Sealer F4 Express, the ultimate internal leak sealer for central heating systems. This market-leading solution quickly repairs microscopic, hard-to-reach leaks and weeps, preventing pressure loss and boiler breakdowns without draining the system.

Why Fernox Leak Sealer F4 Express?

• Rapid Leak Repair: Targets and seals pinhole leaks in 1-24 hours using advanced polymer technology, stopping oxygen ingress for lasting protection.
• No Drain-Down: Doses in 30 seconds via radiator, filling loop, or TF1 Filter, saving time and repair costs.
• Safe & Reliable: Proven to avoid blockages in boilers, pumps, air vents, and heat exchangers, ensuring system safety.
• Eco-Friendly: Non-toxic, recyclable canister with non-flammable compressed air propellant (Fernox Express Barrier Pressure Pack technology) prevents corrosion risks.
• Universal Fit: Compatible with all heating systems, including aluminium.

Key Features

• Fast-Acting: Seals leaks in as little as 1 hour, fully effective within 24 hours.
• Cost-Saving: Eliminates costly drain-downs and invasive repairs.
• Environmentally Safe: Non-hazardous formula in a 100% recyclable can.
• Easy Application: Includes adapters for radiator, filling loop, or TF1 Filter dosing.

How to Use

Apply Leak Sealer F4 Express via radiator, filling loop, or TF1 Filter (adapters included). Pair with Fernox Cleaner F3 and Fernox Protector F1 for optimal system care. Maintain annually for peak performance.

Why Choose Leak Sealer F4 Express?

• Market-Leading: Quickly seals leaks without compromising system components.
• Time & Money Saver: Fast, no-drain application reduces downtime and costs.
• Safe & Green: Non-toxic, corrosion-free, and eco-conscious design.