A boiler breakdown or central heating fault is every homeowner’s worst nightmare – having to deal with a cold house, no hot water and a costly boiler repair or replacement is no fun for anybody.
Due to this, it is of utmost importance that you maintain and take care of your central heating system as much as possible to prevent expensive and inconveniencing breakdowns.
One of the best ways to do this is by using in central heating inhibitor to protect your heating system and reduce the likeliness of boiler issues.
In this guide, we’ll highlight the benefits of central heating inhibitor, explain how it works and inform you of how often it should be changed.
What is Central Heating Inhibitor?
Central heating inhibitor is a chemical liquid that acts as a central heating protector. It is placed into your central heating system to help prevent inhibiting substances such as rust, sludge and corrosion from hindering the performance and efficiency of your home heating.

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Central heating corrosion inhibitor contains a mixture of potassium tetraborate tetrahydrate, along with disodium molybdate, sodium nitrate and 2,2′,2”-nitrilotriethanol.
It is typically pale yellow or clear in appearance and most instructions state that it must be stored in its original container and left in a cool well-ventilated location that is away from direct sunlight.
What are the benefits of central heating inhibitor?
Investing in a central heating protector like central heating corrosion inhibitor can have benefits, these include:
- Prevents corrosion, rust and sludge within the heating system
- Helps to keep radiators working efficiently
- Increased boiler efficiency can help to lower your energy bills
- Saves you money on expensive repairs and boiler replacements
- Boosts the performance of your central heating system
- Helps to prevent boiler breakdowns and faults
- Can prolong the lifespan of your boiler
What does central heating inhibitor do within the central heating system?
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Substances such as rust and sludge can gradually begin to form and collect within your central heating system over time. These materials can begin to impact the performance and efficiency of your heating system and eventually lead to a breakdown.
Central heating rust inhibitor helps to prevent this internal corrosion and keep your boiler functioning effectively for as long as possible. The chemicals within in the heating system inhibitor will work together to break down the sludge in your central heating system and protect it from building up again.
Without central heating system inhibitor, the metals and water that are within your heating system can react with each other and cause rust and corrosion. The presence of these inhibiting substances can force your boiler to work harder in order to provide you with heating and water, causing excessively high energy bills and increasing the likeliness of a breakdown.
How often should central heating inhibitor be changed?
Your central heating inhibitor will need to be changed once a year. Gradually, the solution will dilute and your central heating corrosion inhibitor will begin to lose its effectiveness. You should also be sure to top up your radiator rust inhibitor whenever you drain your central heating system, as some of the solution will be lost in the drainage.
It’s recommended that you get your boiler and central heating system checked by a professional once a year to ensure that it remains in good shape for as long as possible. A yearly service appointment is often a requirement of your boiler’s warranty, so organising annual health check for your system will help to keep you covered. During your heating system’s servicing appointment, your engineer will add central heating boiler inhibitor to your system, as it is included in the service provided.
Here at 247 Home Rescue, we have an expert team of Gas Safe registered engineers who can provide you with a first-class boiler service to ensure that your heating system functions at its best for years to come. We also offer a number of home cover and boiler cover plans which include yearly servicing.
Book a boiler servicing appointment today with one of our expert engineers or take a look at our home cover options for more information.
How to add inhibitor to your central heating system
You don’t typically need the help of a professional in order to add central heating inhibitor to your heating system – it should be a simple DIY task if you feel comfortable and competent enough to complete it.
You can add radiator inhibitor to your central heating system in a number of ways depending on the type of boiler system you have installed. Thus, the process of adding central heating inhibitor to a heat only system will differ to the procedure for adding inhibitor to a combi boiler.
Below we’ll take you through how to add boiler inhibitor to different boiler systems:
Combi Boilers
Combi boilers are the most popular form of heating in the UK, so we’ll start with these systems.
Here’s how you go about adding inhibitor to a combi boiler – firstly, locate a radiator, this can be a towel radiator or a normal one. Before adding the radiator inhibitor, you should ensure that the radiators are cool and that the system is switched off.
If you choose to pour inhibitor into a towel radiator, all you’ll need to do is simply remove the plug at the top and pour the solution in. For normal radiators, you’ll need to pour the central heating inhibitor into the valve where you usually bleed your radiators.
Heat only Boilers
Heat only boilers feature a hot water cylinder and an expansion tank in the loft. For these types of systems, the central heating corrosion inhibitor will need to be poured into the smaller expansion tank. Before you do this, you’ll should ensure that the water is switched off at the mains and you also need to ensure that the tank is clean and free of corrosion or any other inhibiting substances. We recommend giving the cold water tank a good clean before adding in the boiler inhibitor.
System Boilers
If you have a system boiler installed in your home, simply pour the central heating rust inhibitor into the filling loop. Please note, you may need to drain some of the water from the system prior to adding the heating system inhibitor, as water cannot be displaced in a sealed system in order to allow enough space for the extra liquid.
How much central heating inhibitor should I use?
For a central heating system with up to 10 radiators, a one litre bottle of radiator inhibitor should suffice. If you have over 10 radiators in your property, you can add more than this as required.
It is sometimes recommended for you to stick to one brand of central heating inhibitor if possible. Additionally, you should refrain from adding more radiator rust inhibitor than needed to your system, as this can damage filters and will have no additional impact than adding the correct amount would. Always stick to the recommended amount stated on the boiler inhibitor’s instructions.
Upgrading your central heating system
As highlighted, adding central heating inhibitor to your heating system can effectively help to cleanse the system, keep it efficient for longer, and improve performance. However, there’s only so much that central heating corrosion inhibitor can do. If you’re frequently facing issues with your home heating, or if you’ve had your current boiler system for over ten years, it may be time to invest in a new boiler.
A new boiler can provide your home with an enhanced quality of heating and hot water. Not only that, but modern boilers are designed to be highly energy-efficient – it is estimated that a new boiler could help you save up to £190 per year on your energy bills [1]. Furthermore, contemporary boilers are built with a number of innovative features and functions that make everyday home heating a simple task.
If you think it’s time to purchase a new boiler system, 247 Home Rescue could provide you with a first-class boiler replacement at an excellent price. We install boilers from leading brands such as Worcester Bosch, Ideal and Vaillant, and we’ve got the knowledge and expertise to help you find a suitable boiler for your home and needs.
Simply try our free online quote tool today to find the best boiler for your property. You’ll be provided with your free quote in a matter of seconds.
FAQs
What is central heating inhibitor made of?
Central heating inhibitor is composed of a mixture of potassium tetraborate tetrahydrate, sodium nitrate, disodium molybdate and 2,2′,2”-nitrilotriethanol.
How often should central heating inhibitor be changed?
It is recommended that you change your central heating system inhibitor once a year. This is to provide a top up of the solution to your system as it is likely to dilute over time and become less effective. You should also top up your central heating corrosion inhibitor whenever your system is drained.
How to add inhibitor to central heating?
If you’re adding inhibitor to a combi boiler, you can add the boiler inhibitor to a towel radiator via the plug or a standard radiator via a valve. If you have a heat only or regular boiler, you will need to add the rust inhibitor to your expansion tank, which is usually located in the loft. Finally, if you have a system boiler installed, you should add the radiator inhibitor into the filling loop.
What does inhibitor do in central heating?
An inhibitor can help to effectively cleanse and maintain your central heating system. Over time, substances such as sludge, rust and corrosion can build up within your heating system and begin to affect its efficiency and performance – it could even cause a breakdown! Central heating inhibitor is designed to break down these inhibiting substances and help your boiler work more efficiently for as long as possible.
How much is central heating inhibitor?
On average, central heating inhibitor can cost £10-£30 in total. Popular boiler inhibitor brands include Sentinel, MagnaClean, Fernox and Adey.
Where can I buy central heating corrosion inhibitor?
You can purchase central heating corrosion inhibitor from your local plumbing supply store, DIY store or you can buy the radiator rust inhibitor online.
What other measures can I take to protect my central heating system?
As well as adding central heating inhibitor to your heating system, you can also conduct the following:
- Book an annual boiler service appointment for your central heating system
- Flush your radiators with a central heating Powerflush
- Add scale reducer to your heating system to reduce the impact of limescale
- Install a magnetic boiler filter to capture any material or debris that could hinder your heating system.