10 Best Central Heating Leak Sealer in The UK

Last updated on 12/08/2025

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Kudos-Trading - Fernox F4 Express Leak Sealer 400ml Aersol Can Reduces Small Leakage From Your Heating System Of 130 Litres Plumbers DIY Home Owners.

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Why We Love It

Quick and easy application.
Seals small leaks effectively.
Safe and non-toxic.

Main Highlights

Easy application method: Fernox F4 Leak Sealer Express 400ml is designed for a quick, simple, and hassle-free application. With its unique pressurized canister, it can be directly introduced into a heating system without the need for draining or disassembly, saving time and effort.
Seals small leaks effectively: This product is specifically formulated to seal small, inaccessible leaks and weeps which can cause pressure loss in your central heating system. It's an ideal solution for hard-to-reach places where manual intervention is difficult.
Non-toxic and safe to use: The Fernox F4 Leak Sealer is composed of non-toxic, environmentally friendly materials. It's safe for prolonged exposure to the system's components and doesn't pose any risks to the health of homeowners or technicians.
Compatible with all materials and metals: This leak sealer is compatible with all metals, including steel, copper, brass, and aluminum, as well as materials such as plastic and rubber, found in heating systems. This wide-ranging compatibility ensures a versatile application across various system configurations.
Does not cause blockages: The F4 Leak Sealer is specially designed to seal without clogging. It won't block valves, air vents, or pumps, ensuring your heating system continues to operate efficiently even after application.
Long-lasting effectiveness: Once applied, the Fernox F4 Leak Sealer Express provides a long-term solution to leaks. Its robust formulation allows it to withstand the regular functioning of your heating system, maintaining its sealing properties over an extended period.
Helps in reducing energy consumption: By effectively sealing leaks and improving system efficiency, the Fernox F4 Leak Sealer Express can help reduce energy consumption. This can lead to a significant reduction in energy bills and is a step towards more sustainable energy usage.
Compatible with other Fernox products: The Fernox F4 Leak Sealer Express 400ml is fully compatible with other Fernox products, including the entire range of Fernox inhibitors, providing comprehensive protection for your heating system.

CosWarm CW4 Central Heating Leak Sealer - Treats Up to 18 Radiators - Stops Leak - Boiler Leak Repair & Sealant - Stops Minor Leaks & Weeps, Fixes Pressure Loss & Leaking Pipes - Underfloor Heating

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Why We Love It

Seals leaks, saves time.
Protects metals, safe for environment.
Easy application, convenient usage.

Main Highlights

STOPS SMALL LEAKS & FIXES PRESSURE LOSS: CW4 Leak Sealer seals all the small and inaccessible leaks, thus saving time and money in draining down and repairing cost. Our boiler leak sealant also helps in fixing pressure loss due to minor leaks from central heating systems.
SUPER CONCENTRATED FORMULA: Our boiler and central heating system leak stopper can treat up to 18 single radiators, i.e., a 150-litre system. It is easy to use, just pour it in the system according to the instructions and let it work.
HARMLESS FOR METALS: There are many leak sealant chemicals that are not friendly when they come into contact with metals. CW4 Leak Sealer liquid is suitable for use with all the metals and materials, including steel, ferrous metals, copper and aluminium.
CONVENIENCE AT ITS BEST: Our leak sealer and stopper makes minor repairs in the boiler a breeze. It does not interfere with the working of your central heating systems and you won’t have to shut down the systems before or while using it. The product can be left in the system permanently.
SAFE FOR YOU, THE BOILERS & THE ENVIRONMENT: Our non-toxic radiator leak sealer is a safer alternative compared to other toxic, chemical formulas. As it is biodegradable, it won’t harm Mother Nature either. Safe to use around people, the environment and your heating systems.

Kudos-Trading - Fernox F4 Leak Sealer 500ml Liquid Seal for Central Heating Pipe Work Leaks Water Underfloor Heating Non-Corrosive Non-Toxic Compatible with Most Heating Systems Long-Lasting Seal

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Why We Love It

Ease of use guaranteed.
Effective sealing performance.
Environmentally friendly solution.

Main Highlights

Easy-to-use formula: Fernox F4 Leak Sealer is designed for quick and hassle-free application. It comes as a ready-to-use liquid that doesn't require any additional mixing or preparation, making it convenient for homeowners and professionals alike.
Effective sealing performance: This high-quality leak sealer is engineered to efficiently and reliably seal small, inaccessible leaks and weeping joints in hydronic heating systems. Its advanced formulation ensures a long-lasting and dependable sealing effect on various materials, including metal, plastic, and composite pipes.
Compatible with all metals and materials: The versatile Fernox F4 Leak Sealer is suitable for use in systems containing a wide range of materials, such as copper, brass, steel, iron, aluminium, and plastics. This makes it a perfect solution for diverse heating systems, regardless of their construction and components.
Non-toxic and environmentally friendly: Developed with safety and sustainability in mind, Fernox F4 Leak Sealer is non-toxic, non-corrosive, and non-flammable. Its eco-friendly formulation means that it is safe for use in all domestic heating systems and poses no harm to the environment.
Rapid dispersion and circulation: The liquid formulation of the Fernox F4 Leak Sealer allows for quick and even distribution throughout the system, ensuring that the product reaches all areas where leaks may be present. This rapid circulation ensures effective sealing and minimal downtime for your heating system.
Effective in both open and closed systems: Whether your heating system is an open-vented or sealed system, the Fernox F4 Leak Sealer is designed to deliver optimal sealing performance. Its versatility makes it a go-to solution for a wide range of system types.
Does not cause blockages or restrictions: Fernox F4 Leak Sealer's unique formulation prevents the formation of any solid residues, ensuring that it will not cause blockages or restrictions within the heating system. This means you can trust it to deliver excellent sealing without compromising the efficiency of your system.
Long-lasting protection: With its superior sealing performance and compatibility with a wide range of materials, Fernox F4 Leak Sealer provides long-lasting protection against leaks and weeping joints. This helps extend the lifespan of your heating system and minimize the need for costly repairs.

LavaTap – Fernox F4 Express Leak Sealer 400ml - Central Heating Leak Sealer Spray for Radiator and Pipe Leak Repair, Stop Leak Solution for Sealed Systems

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Why We Love It

Quick and easy application.
Safe for all heating systems.
Effective for hard-to-reach leaks.

Main Highlights

30-Second Application: Applies in just 30 seconds with no system drain-down required, helping you quickly seal leaks and restore pressure with minimal disruption.
Safe for All Heating Components: This radiator leak sealant is non-toxic and safe for boilers, pumps, air vents, and heat exchangers. Won’t cause blockages, making it ideal for sealed and combi systems.
High System Coverage: One 400ml can treats up to 130 litres—around 16 radiators or 250m² of underfloor heating—providing wide coverage for minor leaks in sealed systems.
Radiator Stop Leak Performance: Seeks out inaccessible micro-leaks caused by air ingress and seals them without blocking heat exchangers or pumps—ideal as a radiator stop leak for central heating systems.
Low-Impact Leak Sealant Spray: Powered by compressed air instead of harmful propellants, this leak sealant spray is non-flammable and comes in a fully recyclable can.
For Trade or DIY Maintenance: Trusted by heating engineers and DIY users alike, this leak sealer makes in-system leak repair quick and hassle-free—ideal for maintaining pressure in sealed systems.

Fernox Central Heating Leak Sealer F4 Express 265ml

Why We Love It

Doses in 30 seconds.
Simple and mess-free.
Seals most leaks.

Main Highlights

Quick and convenient – doses in 30 seconds
Simple to use with no mess
Saves time and money on draining down and repairing
Seeks out and seals most weeps and leaks
Non-toxic, environmentally friendly formulation

Kudos-Trading - Fernox F1 Protector 500ml 56599 Protector F1 Central Heating and Water Underfloor Heating Corrosion Protection limescale Prevention System Efficiency Long-Lasting Protection

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Why We Love It

Prevents corrosion and limescale.
Cost-effective heating system solution.
Safe, non-toxic, eco-friendly.

Main Highlights

Fernox Protect F1 is a central heating system inhibitor that prevents corrosion and limescale buildup. It is suitable for use in all types of central heating systems, including those with non-ferrous metals.
It comes in a convenient 500ml bottle that can be added directly to your central heating system without the need for complicated installations or special equipment.
Fernox Protect F1 is a cost-effective solution that can help to extend the life of your central heating system, improve energy efficiency, and reduce the risk of costly breakdowns and repairs.
It is non-toxic and environmentally friendly, making it safe to use around children and pets. Fernox Protect F1 is compatible with all types of heating system water, including hard and soft water.
It has been extensively tested and proven in the field, and has been awarded certificate for corrosion inhibition. It has been tested to Astm standards for corrosion, scale, and biocidal performance, ensuring reliable and effective results.
Using Fernox Protect F1 can help to reduce energy bills and save money in the long run. It is a highly effective solution for central heating system protection and is trusted by homeowners, landlords, and professional heating engineers.
Fernox Protect F1 is a central heating system inhibitor that provides protection against corrosion and limescale buildup It is suitable for all types of central heating systems, including those with non-ferrous metals
The product comes in a convenient 500ml bottle that can be added directly to your central heating system without the need for special equipment Fernox Protect F1 helps to extend the life of your central heating system, improve energy efficiency, and reduce the risk of costly breakdowns and repairs
It contains a blend of corrosion inhibitors, scale inhibitors, and biocides that create a protective barrier against rust and scale buildup Fernox Protect F1 is non-toxic and environmentally friendly, making it safe to use around children and pets
Fernox Protect F1 has been extensively tested and proven to provide reliable and effective protection against corrosion and limescale buildup It has been awarded the Bsria certificate for corrosion inhibition and has been tested to Astm standards for corrosion, scale, and biocidal performance.

Sentinel Leak Sealer 1L, Seals All Minor leaks and Weeping Joints in Heating Systems, Suitable for All Metals Including Aluminium, Will not Cause blockages in The Heating System

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Why We Love It

Seals all minor leaks.
Compatible with all metals.
Works with other Sentinel products.

Main Highlights

Ideal for sealing small leaks or weeping joints on all types of indirect central heating systems
Seals small leaks or weeping joints on all types of indirect central heating systems
Seals all minor leaks
Compatible with other Sentinel products
Suitable for all metals including aluminium

Everbuild P32 Central Heating System Leak Sealer, 500 ml

Why We Love It

Quick leak sealing solution.
Prevents system blockages effectively.
Works within 1-24 hours.

Main Highlights

Rapid, internal leak sealer that is designed for central heating systems suffering from small, inaccessible leaks and weeps which may cause pressure loss
Once added to the system, the product locates the area of water loss and forms a soft barrier to permanently seal the hole
Effective within 1 - 24 hours and has been tested and proven to prevent blockages or restrictions in system components without blocking valves, pumps or air vents
Compatible with all metals
This 500ml bottle will treat approximately 60 radiators

FERNOX Central Heating Leak Sealer F4 Express 400ml - Fast Results - 30 sec - (Replacement 58232)

10% Off

Main Highlights

Item comes with 3 nozzles for application

Corgi TRIPCON5-C Concentrated Central Heating Leak Sealer - Clear

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Why We Love It

Fixes inaccessible leaks easily.
Won't block circulator pumps.
Handles without safety concerns.

Main Highlights

To seal inaccessible leaks and weeping joints
Reduces pressure Loss in sealed systems & does not cause blockages in circulator pumps or air vents
Non-acidic, non-caustic - safe to handle
Concentrated 500ml treats up to 10 radiators - a typical central heating system
Controls scale and maintains boiler efficiency

8.7

Excellent

We scanned 254 products

We reviewed these offers relevant to the Central Heating Leak Sealer within online retailers such as Amazon, eBay and other local retailers, ensuring we covered all major brands and models. The products we selected come from trusted brands like Kudos-Trading, CosWarm, LavaTap, Fernox, Sentinel, Everbuild, Corgi, all of which have a reputation for consistently delivering high-quality products that users love and innovative approaches for function & design.

For the best Central Heating Leak Sealer in the market, we considered we took a deep dive into 1271 online reviews , focusing on elements like user satisfaction, performance in real-world conditions, and long-term reliability. Our ranking also evaluates each review’s relevancy, authenticity, up-to-dateness and depth so that the comparison is more sound.

We concluded that:

The clear winner of our analysis is Kudos-Trading - Fernox F4 Express Leak Sealer 400ml Aersol Can Reduces Small Leakage From Your Heating System Of 130 Litres Plumbers DIY Home Owners.. We love many things about this product by Kudos-Trading. What sets it apart from the competition is Quick and easy application, Seals small leaks effectively, Safe and non-toxic.
The best value product for most shoppers and where user satisfaction is continuously the highest is CosWarm CW4 Central Heating Leak Sealer - Treats Up to 18 Radiators - Stops Leak - Boiler Leak Repair & Sealant - Stops Minor Leaks & Weeps, Fixes Pressure Loss & Leaking Pipes - Underfloor Heating by CosWarm based on online reviews by bloggers, experts and online shoppers.
The biggest bargain at the moment for Central Heating Leak Sealer and the best cost-to-value ratio is FERNOX Central Heating Leak Sealer F4 Express 400ml - Fast Results - 30 sec - (Replacement 58232)at Fernox with a 10% discount.
Our list of the best Central Heating Leak Sealer is updated regularly to reflect new releases and changes in product availability, so be sure to check back often for the latest rankings and discounts.

10 Best Central Heating Leak Sealer in The UK

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We scanned 254 products

We concluded that: