Central Heating Inhibitor: What is it & How Does It Work?

James Elston
Written by James Elston
Updated on 17th May 2024
Posted on 15th May 2024
Topic: Boiler Advice
central heating inhibitor

When it comes to boilers for your home and their various components, most of us simply want them to work when we need them most.

We would be happy to leave the language and jargon surrounding boilers to the professional engineers to understand, as long as our homes stay warm and welcoming on a winter day and our showers hot (even for the family member last in line to use it).

Along those lines, “central heating inhibitor” sounds like some sort of component buried deep within a boiler that is installed in a factory and never seen by the homeowner. However, sounds can be deceiving in this case as central heating inhibitor is not a component at all!

What is Central Heating Inhibitor?

Central heating inhibitor is not a part, component, or physical piece of the boiler or heating system. Rather, it is a compound liquid used as a central heating treatment to make your boiler and system work effectively. It does this by reducing the amount of corrosion that takes place in the system.

This compound is made up of:

  • potassium tetraborate tetrahydrate
  • sodium nitrate
  • disodium molybdate
  • nitrilotriethanol

The result is a clear or sometimes pale yellow liquid that works to clear a thick and sludge-like substance that can accumulate both in your system pipes and at the foot of each radiator.

What is central heating or radiator sludge?

Even the tidiest, most fastidious homeowners are not immune to the possibility of this sludge building up in their home heating systems. This build-up occurs because the heating system uses metal pipes that are susceptible to rust and corrosion over time.

All this central heating and boiler corrosion can cause problems. That rust, along with dirt, limescale, and other debris, ultimately forms the sludge that travels through your system pipes and ends at the foot of each radiator. Along that path, this goopy mixture can build up and prevent water from passing through the pipes smoothly and efficiently.

This blockage can start as a minor problem but grow into a much bigger one affecting your boiler and heating system performance. Over time, the build-up can also cause serious damage and cracks to your pipes.

Central heating inhibitor is the key to beating the negative consequences of this central heating system sludge.

Adding Central Heating Inhibitor to Your System

To prevent boiler corrosion and extend the life of your central heating and ensure its long-term performance is not affected by debris build-up, you need to add central heating inhibitor.

If you have never maintained a heating system before (perhaps you are a first-time homeowner), we have simple guidelines outlined below with everything you need to know.

1. Turn It Off

The most important thing to bear in mind with central heating inhibitor is that you must first turn your system off. It can be dangerous to add this compound while your heating system is in operation.

Read the manufacturer guidelines closely and carefully to be sure you have your system off and follow the specific instructions for adding the central heating inhibitor.

2. Determine the Type of Heating System and Add the Compound

Before you pour central heating inhibitor into your system, you need to be aware of the slight differences in instruction based on the type of system in your home. Yours may be what is known as an open-vented heating system, or it may be a sealed heating system. Additionally, some heating systems use combi boilers. We will touch on those as well.

The instructions will differ slightly based on which one of these systems you operate in your home.

If you are working with an open-vented system, you need to be aware that there is more than one tank and ensure you add central heating inhibitor in the correct one. The expansion tank, which will be the smaller one, is where you will pour the compound into your system. You will also need to clean the tank, which can be where some problems start in your system.

If you are working with a sealed system, there is less room for error as there is only one place to add the central heating inhibitor: through the boiler filling loop.

If you have a combi boiler, you will add the central heating inhibitor through a plug or a bleed screw radiator valve. You will want to be sure the system is off before you pour the compound into the radiator valve. Once you finish adding the compound and replace the plug, turn on the system to force it to spread throughout the pipes.

How Much Central Heating Inhibitor will My System Require?

To determine how much central heating inhibitor you need, you will need to consider the specific manufacturer instructions on the brand you are using and the size of your heating system.

In most cases, a litre of central heating inhibitor will be enough to work on 8 to 10 radiators. If your system has more than ten radiators, you may need to use two bottles of central heating inhibitor to be effective.

The key thing to remember when it comes to the amount is you do not want to go overboard, Using too much central heating inhibitor could actually cause damage to your system, and it is ultimately “damage” you were trying to repair by using it, so you want to avoid making your system any worse.

Too much central heating inhibitor in your system could result in damage to its magnetic filters. It is also a waste of money and the product to try and overdo it: you will not achieve a better result this way. Be sure you use only the recommended volume of central heating inhibitor for your system and the number of radiators.

When and How Often Central Heating Inhibitor Should be Used

It may seem tempting to use central heating inhibitor often, but this should only be applied to your system on an annual basis.

You will want to refer to both the inhibitor manufacturer’s instructions and your system manual, but the once-yearly wave of inhibitor is what you will find most professional engineers recommend for heating systems.

Using the product more often can ultimately be a waste of time and money, and as indicated above, could do more harm to your heating system than good.

Make a note on your calendar to do this along with other home maintenance chores you might do annually, such as changing batteries out in smoke detectors.

Central Heating inhibitor as a Prevention Tool

Central heating systems and boilers are not cheap and not something you want to replace often. Just as regular maintenance on your vehicle helps it stay roadworthy longer, a central heating inhibitor will prevent problems affecting your heating system’s performance.

The central heating inhibitor will break down the sludge as it starts to form in your pipes and radiators, which could cause major problems if left to build up without intervention. Some of these problems may include

  • Lack of Heat: sludge and blockages could mean your radiators or showers are not hot, making for a particularly miserable time on a frigid day. Central heating inhibitors can help prevent the blockages that would lead to no heat.
  • Rust-damaged pipes: Central heating inhibitor can work to prevent rust build-up, which ultimately damages your pipes and your heating system.
  • Pressure Changes: When pipes are damaged due to debris build-up, you may see a drop in boiler pressure. Blockages and leaks are caused by the build-up of sludge. Central heating inhibitor can help prevent these changes in pressure from debris-damaged heating systems.
  • Performance Affected by Impure Water: When debris is left to build up in a boiler tank, you may find that your system no longer heats water as effectively.

Inhibitors, Filters and Heating Systems

A central heating inhibitor application once a year will aid and improve the performance of your heating system. If you are interested in other ways to produce a better result from your heating system, you might also consider magnetic filters as an option.

What is a Magnetic Filter?

A magnetic filter is a special filter for a boiler that works to catch debris with a magnetic force. For example, you may have small metal shards in the water from areas where your pipes have rusted, and the magnetic filter acts to catch those, removing them from your water supply.

This type of magentic filter slows the accumulation of sludge that will collect in your pipes and radiators.

Bear in mind that depending on the type of system you have in your home, you may require the assistance of a professional engineer for magnetic boiler filter installation.

Are Limescale Reducers the Same as Central Heating Inhibitors?

Some homeowners think limescale reducer is the same as a central heating inhibitor. While the two are indeed similar, they are not the same.

Limescale reducer, as the name implies, targets limescale in your system. If limescale is your primary issue, then scale reducer may work perfectly to improve your system’s performance. However, in many cases, you will need a central heating inhibitor, which targets debris build-up of debris beyond just limescale.

If you have any doubt about which product is best suited for the care and maintenance of your system, ask a professional engineer during your annual boiler service.

Does My Warranty Cover Debris & Sludge Build Up?

The build-up of debris and rust in your pipes and radiators is a part of the normal wear and tear of operating a heating system, and as a homeowner, you do bear some responsibility for maintaining your system.

It is important to read your boiler warranty carefully, especially before purchasing a new or replacement boiler and ask the manufacturer or salesperson specifically about maintenance and central heating inhibitor products they recommend.

A carefully maintained and cleaned heating system will run more efficiently, saving you on heating bills in the long run. While heating systems are a considerable expense for homeowners, you can invest last longer with proper care and a good warranty.

Do not skip the annual service or skimp on things like central heating inhibitor or you will likely replace your boiler sooner than you (or your bank account) would like.

If boiler replacement is something you are considering, you should also look into boiler installation, as getting a high-quality installer is very important for your boiler’s efficiency. As is getting the best combi boiler to suit your heating needs, so researching this can be another vital step to take.

For more useful advice on boilers and heating systems check out all of our guides here.

Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 15th May 2024
Topic: Boiler Advice

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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