HeatingForce is reader-supported. When you buy through links on our site, we may earn an affiliate commission. Learn more

How to use a lockshield valve to fix a cold radiator

If you have ever wondered what a lockshield valve is for, wonder no more. In this guide, we tell you everything you need to know about them and also their main purpose. If you have cold radiators and your system needs rebalancing, lockshield valves are crucially important.

Lockshield valve

On these cold winter nights, there is nothing worse than going into a cold room in your house and finding the radiator isn’t working properly. Perhaps the only thing that tops being cold in your own home, is the prospect of shelling out a significant fee for a plumber or heating engineer to fix the problem.

You’ve probably Googled ‘how to fix a cold radiator’, had a go at bleeding it, and when that hasn’t worked and you’ve started reading about lockshield valves and balancing radiators and got so confused that paying for a professional seems to be the only option.

You’ve come to the right place. Fixing a cold radiator is actually surprisingly easy and certainly within the capabilities of most basic DIYers. Lockshield valves are nothing to be scared of and actually the central part of the very simple process of balancing your radiators that, more often than not, will be able to fix cold radiators and make your entire house toasty-warm this winter.

If you want to find out everything you need to know about lockshield valves, balancing radiators, and making your home warm again, just keep on reading.

What is a lockshield valve?

Radiator lockshield valve

A lockshield valve is one of the valves on a radiator. It is usually covered with a plastic cap. The word lockshield is a reference to this cap. It means that once a valve has been adjusted, the cap is secured over it to stop the valve being accidentally knocked or altered.

The cap to a lockshield valve can usually be removed by either pulling it or unscrewing it. On some models, the cap is screwed on and you will need a screwdriver to unscrew it.

Once the cap has been removed, the valve looks a little like the end of a spindle. This spindle can be either square or half-moon shape. It can usually be adjusted by hand but if the radiator is older, you might find you need an adjustable spanner to move it.

A lockshield valve can be used to adjust how quickly a radiator takes to warm up. By opening the valve, more hot water can flow through the radiator meaning it will warm up faster. By closing the valve, the flow of hot water is reduced and the radiator will not warm up as fast.

Most people don’t even know what a lockshield valve is, never mind how to use one. But they are actually a really useful feature on a radiator to allow you to adjust how quickly an individual radiator warms up.

Boiler problems?

Get a boiler quote here

Balancing radiators vs bleeding radiators

The one bit of radiator maintenance most people have heard of, and a lot will do for themselves, is bleeding a radiator.

Bleeding a radiator involves using a special radiator bleed key to unlock the top of a radiator and release any air that may have got trapped inside. If there is air trapped in a radiator, it will not be able to fill up sufficiently with hot water and will therefore not be hot enough.

Bleeding a radiator is a simple task and requires no more than a bleeding key, a bit of kitchen roll, and about ten minutes of your time. If your problem is being caused by air trapped in a radiator, bleeding should resolve it.

But more often than not, cold radiators are not caused by trapped air. A far more common problem is one of an unbalanced heating system. This means that some radiators are filling up with hot water much faster than others. This means they get hotter faster and the rooms they heat subsequently seem far warmer than others in the house.

Balancing your radiators sounds like a complex task, but it is actually very simple. Most DIYers can rebalance their radiators. All you need is a couple of tools, a spare couple of hours, and ideally a few willing helpers (although this isn’t absolutely essential).

How to balance your radiators to fix a cold radiator problem

To get ready for the job of balancing your radiators, you will need to gather together a few tools that are needed for the job. So before we begin, pop out to your shed and bring in the following key items:

  • A lockshield valve key (if you have one)
  • A radiator bleed key
  • A screwdriver
  • A digital thermometer or multimeter with thermometer

You may not need all of these depending on the type of radiators and valves in your home. But to make balancing your radiators as quick and simple as possible, it is a good idea to dig these few things out.

Step One: Switch off your home heating system

The first thing you will need to do is switch off your home heating systems and wait until the system has cooled down. As you will see, this is an essential step to help you work out which radiators heat up the fastest and which are the slowest.

Step Two: Bleed your system

As we have explained, bleeding your radiators solves a separate issue. But if you do have air in your radiators it can also affect the speed at which they heat up. SO, if you haven’t recently done it, while the system cools down, it is well worth going around all your radiators and bleeding them all to make sure no air pockets are going to affect your rebalancing.

Step Three: Preparing your radiators valves

To rebalance your radiators you will need to have access to your lockshield valves so this is the time to remove the caps over the valves.

As we have already explained, some of these will be push caps, some will be screw caps, and some may need a screwdriver to be removed. It is likely that all your radiators will have the same type of caps but if you have changed some individual radiators, they might be different.

Whatever type of caps you have, removing them should be a simple job and only take a few minutes.

Step Four: Open your radiator valves

Once the system has cooled down, you will need to open your lockshield valves. To do this, you will need to turn them in an anti-clockwise direction (to the left).

This can usually be done by hand, but if your valves are a bit stiff, use your lockshield valve key instead.

Step Five: Switch the heating back on and start measuring

Once all the valves have been unlocked, it is time to switch your heating system back on.

As it warms up, you will need to measure the speed at which each radiator is warming up. This is where it can help to enlist the help of friends and family, otherwise, you will be running frantically from one room to another trying to note the temperatures of all your radiators yourself.

It is normal for those radiators closest to the boiler to heat up the quickest. But if your system is unbalanced this may not be the case. At the end of this step, you should have a list ranking all your radiators from the quickest to warm up to the slowest.

Step Six: Begin with the fastest-heating radiator

The rebalancing begins with the fastest-heating radiator in your house. Close the lockshield valve on this radiator by turning it in a clockwise (right) direction. Once it is closed, open it up again by exactly a quarter of a turn.

Step Seven: Measuring the temperature

Now use your digital thermometer (or multimeter with thermometer) to take the temperature from the pipework next to the lockshield valve.

After that, measure the temperature from the pipework on the opposite side of the radiator. If your radiator is a newish model, this will be next to the thermostatic valve.

Keep measuring these two temperatures until the difference between them is exactly 12°c. When it gets to this level, close the lockshield valve again.

Depending on how unbalanced your system is, this process can take a fair few minutes so be patient with this step.

Step Eight: Repeat this process with your other radiators

Now is the lengthiest stage of the process. You will need to repeat the temperature-measuring stage for all of the radiators in your home. You should work down your list from the second-fastest radiator to heat all the way down to the slowest and ensure the temperature difference between the two pipes is exactly 12°c.

With some of the slower radiators, if the process is taking too long, you can open the lockshield valve up more to adjust the temperatures. In some cases, we even ended up unlocking the valve completely again.

Result: A balanced heating system

Once every radiator in your home has been rebalanced, the problem of cold radiators should have been resolved. The hot water from your boiler should be reaching all of them at equal speed and your whole house should warm up at the same time and be pretty much the same temperature.

What to do if this doesn’t solve the problem?

The majority of cold radiator issues we have come across can be resolved by rebalancing your radiators. An unbalanced system is a common problem that most people don’t know about. But as we have seen, it is easily fixed.

However, if rebalancing your radiators doesn’t fix the issue of cold radiators, there could be another underlying problem that is resulting in the problem.

The best thing to do at this stage is to consult with a plumber or heating engineer. With any luck, there might be a simple issue with your pipes, your radiators, or your boiler that they can resolve with a few adjustments or a new part. But in the worst-case scenario, you may find that you need a new boiler.

How to get the cheapest boiler and the lowest installation costs

Being told you need a boiler can be a real blow. Most people believe boilers are expensive to buy and costly to install and will be bracing themselves for a bill for several thousand pounds.

It doesn’t have to be that way. While boilers can be expensive to buy and costly to fit, there is a website e that can offer you a great deal on a high-quality new boiler and give you great installation rates too. We recommend you try HEATABLE.

HEATABLE are a unique online boiler quotation and installation service. They saw a gap in the market for a fast online boiler quotation and installation site and teamed up with manufacturers to provide the best prices even if it’s a Worcester Bosch or a Viessmann boiler.

Worcester Bosch Greenstar i from Heatable

When you visit the HEATABLE website, you will be asked to fill in a 90-seconds form containing all the details about your home, your existing heating systems, any problems you have had, and what you want from a new boiler. It will then offer you the most competitive quotes possible for your individual home and heating needs.

HEATABLE will also save you money on your installation costs. Its installation prices are, on average, a third cheaper than those offered by your local heating engineer. Even better, you won’t have to wait for weeks to get your new boiler either. HEATABLE can install it as quickly as the following day.

While HEATABLE specialises in gas boilers, they also provide LPG, oil or electric boilers, too. If this is what you need, just contact HEATABLE directly and their helpful customer support team will be happy to assist.

Viessmann Vitodens 050-W from Heatable

If you are still concerned about the upfront costs of buying a new boiler, they also offer some exceptional finance options. These start from just £12.94 per month, which is unbelievably low for a boiler.

Don’t just take our word for it

If you want to see what some other customers think of HEATABLE before trying them, look no further than Reviews.co.uk.

HEATABLE has a trust score of 4.92 out of 5 from more than 2,000 reviews, with 99% on-time deliveries and 98% for accurate and un-damaged orders.

That proves HEATABLE is one of the most trusted boiler sales and installation sites in the UK. And we may add, they have the best prices, too.

Radiator Lockshield Valve: Summary

A lockshield valve is the part of a radiator you look at every day without ever really knowing what it is for. In this article, we have answered this question and also explained how important a lockshield valve is to the main way of fixing the problem of a cold radiator.

This process is known as balancing your radiators and we have provided a simple step-by-step guide for you to do this at home for yourself, without the need to call out for an expensive plumber or heating engineer.

If balancing your radiators doesn’t solve the problem, then you will have to do this and there is a small possibility you might need a new boiler. If this is the case, don’t panic. We have got your back there too and have recommended HEATABLE as a site to get you the cheapest prices for both a high-quality new boiler and a full installation.

Can you think of any other good uses for the lockshield valve not discussed in this guide? How was your experience of balancing your radiators? Do you know any other tips for fixing cold radiators? We always welcome the input of readers in trying to solve these everyday problems so why not share your thoughts and experiences in the comment box below?

Avoid Expensive Breakdown Costs
Boiler Replacement Promise: If it's under 7 years old and we can’t repair it, we’ll replace it.
Try YourRepair. From £9/mo
All plans include: annual boiler service, all parts and labour, unlimited support and 24hr helpline.

Fix things and tutorials

Get a Boiler on Finance

The best pay monthly packages available

Read guide
Heatable Boiler Replacement

Want a new boiler from HEATABLE?

Read guide
WarmZilla Boiler Replacement

Want a new boiler from WARMZILLA?

Read guide
Boiler Installation Costs

Confused about new boilers and their costs?

Read guide