Are you a trader?



Sign Up

How To Put Leak Sealer In Central Heating System

How To Put Leak Sealer In Central Heating System
Written By: | Interiors Specialist
Last Updated Jun 4,2024

Have you found a small leak in your central heating and are unsure how to put leak sealer in your central heating system? Read our expert step-by-step guide to find out exactly how to do it.

How Does Central Heating Leak Sealer Work?

Does central heating leak sealer work? Yes it does! A leak sealer is a liquid that forms a polymer seal over pinhole leaks in a central heating system, effectively stopping any micro pipe leaks you may have.

To apply, simply pour the sealant solution directly into the central heating tank or through the top of a radiator. The leak sealer and filtered water will then flow through your system, preventing further water loss and damage.

Plumber Checking Pipes Before Adding Leak Sealer In

How To Add Leak Sealer To Central Heating System?

  1. Firstly, we recommend you check your central heating system is turned off completely by shutting down the boiler system.
  2. Next, it’s time to drain the central heating system, open the drain valve at the bottom of your boiler or lowest part of the radiator and remove a cup or two’s worth of water.
  3. Then pour in the leak sealer mixture into the heating system. Start with adding a small amount of leak sealer into the towel rail or magnetic filter.
  4. Once completed, you can then top up your central heating system
  5. Restart your boiler and fire up your heating system once more. After filling the system, you can proceed to bleed air from all the radiators or use magnetic filters.

Now you know how to add a leak sealer, you might be wondering what is the best central heating leak sealer on the market? There are a variety of leak sealers on the market, a well recommended choice would be the Fernox F4 Leak Sealer which is suitable for a wide variety of materials including brass, iron and copper based systems.

Central Heating Leak Sealer Getting Poured Into Towel Rail


Will Central Heating Leak Sealer Work On A Boiler?

Yes, sealer will work on a boiler, but it is best to get it fixed soon after as it will only work for so long.

How Do I Find A Leak In My Central Heating System?

A typical way of finding a leak in your central heating system is when you see a huge pressure drop in your system, this drop in pressure will show up on your boiler info dashboard. Another way to find leaks is when you see error warnings flash up on your boiler dashboard. For a more in-depth answer to this question, check out our guide on how do I find a leak in my central heating system.

What Is The Highest Temperature Central Heating Leak Sealer Can Deal With?

It depends on the sealant used but it can withstand very high temperatures, typically up to 194°F or 90°C.

Should I Use A Leak Sealer On My Central Heating?

Yes, absolutely, a leak sealer is a great way to stop those small micro leaks in your heating system and can save you money in the short term.

Can You Help On How To Add Leak Sealer To Combi Central Heating Systems?

Yes, when adding sealant to a combi boiler that is open vented, you place it through the feed and expansion tank and for a sealed combi boiler follow the step by step above!

How Much Leak Sealer Should I Add To My Central Heating System?

If you have a standard sized central heating system, it’s recommended you use around 1 litre of leak sealer. If you have a larger system we recommend doubling it to 2 litres.


Interiors Specialist

Ollie is your guru for all housing interior inspiration, top tips, and new trends. The born & raised northerner has a keen eye for modern and stylish-looking interiors and is constantly on the lookout for the newest and best looks to suit your style.