Are your radiators hot upstairs and lukewarm downstairs? If they are, this means that your radiator system is out of balance and usually when most people read that, they panic and start playing with the valves to get it right. One question that comes up a lot is “Should a lockshield valve be fully open?” Well, it is not quite as simple as that! The lockshield valve should be set to a degree that will allow the radiator or radiators to maintain their desired temperature. This can vary from one building to another, and there are many factors that go into determining this setting. In this article, we will discuss what those factors are as well as how you can determine your ideal lockshield setting and how to balance your radiators for maximum efficiency in your own home.

Lockshield Valve

What is a Lockshield Valve?

A lockshield valve is a simple device used to control the flow of water in and out of your heating system. Located near the top, between the home’s pipes and radiators or baseboard heaters, lockshield valves are usually covered with a plastic cap and are used to balance the heating system. A Lockshield valve is used to adjust how quickly a radiator takes before warming up – opening means more hot water flows through quicker whereas closing slows down the heating process, so things do not get too hot too fast.

Balancing the heating system in this way, allows all of the radiators in the home to heat up at the same rate.

Should Lockshield Valves be Fully Open?

The answer is no, lockshield valves will never be fully open unless you are just about to re-balance the whole heating system. When it comes to balancing radiators, there is no one setting fix-all for the lockshield valves. There are a few variables that come into play such as how many radiators are in the home, the water pressure, and the distance in the heating loop between your first and last radiator. Luckily, there is a process that can be followed to ensure that you are able to balance your own radiators without having to call in a professional to do it for you.

Lockshield Radiator Valve
Lockshield Radiator Valve

How to Balance Radiators

The first step to balancing radiators is checking the manual. The manufacturer may have its own process for getting them in balance, and it is important to follow those steps before trying anything else. If there is not a specific process outlined, or if you have already followed it but have not had any luck with your radiator temperatures still being uneven, follow our steps below. Balancing radiators must not be confused with bleeding radiators. Bleeding a radiator is the process of removing air from the system to allow the hot water to circulate therefore heating the home.

Balancing radiators is the process of using the lockshield valves to regulate the water flow to each radiator to ensure that they all heat up at the same time.

What You Need

It would be handy if you had another pair of hands or a family member to help as this will make things much easier on yourself when checking various radiator temperatures – doing this alone can be exhausting. There are a few tools mentioned below to make your life a lot easier when balancing your radiators too. You may or may not need them all depending on your exact fittings but in general, you will need:

• Lockshield Key
• Radiator Bleed Key
• Screwdriver
Digital Thermometer (Amazon link – opens in a new tab)

Step 1 – Turn Off Your Heating System

First things first. Turn off your heating system and if it has been on, you will need to wait until it has completely cooled before moving on. Starting the system from cold is an important step in seeing which radiators heat up the fastest and which ones are particularly slow.

Step 2 – Bleed the System

To balance your rads, you will need to bleed them first – this is where the bleed key comes in if you are not sure how to do it, we have instructions just for you here. Having air in the system can affect the way the radiators heat up, so it is a good idea to go around and bleed all of the radiators. Luckily, this can be done whilst the system is cooling off.

Step 3 – Open All of Your Radiator Valves

When we say all, we mean all radiator valves. This means, opening (anti-clockwise) the lockshield valves and also the manual valves or TRVs if you have them. We need to do this so that we have an unrestricted flow of water going through our system so that we are able to measure which radiators are heating up the fastest.

Note: If balancing an existing system, the lockshield valves may not have been touched since installation so they may have become very stiff – in comes the lockshield valve key, or adjustable spanner – whichever suits you.

Step 4 – Measuring

The fun bit! Well, probably not so much but this is why it is good to have another pair of hands or a family member to help you. With all of the system’s valves open, you will want to go ahead and turn the system on and measure how fast each radiator is heating up. There is no measurement scale, it is just a case of logging an order of how the radiators are heating. Now you see why the extra pair of hands helps! If not, you should be suitably tired from running around the house so turn the system back off and make a cup of tea.

Step 5 – Temperature Readings

Next up comes the trickiest bit but it is still relatively easy to manage for most people. By now, the system should have cooled again, and you should be nicely rested – we are nearly there so do not worry.

  • Now you will want to turn the system back on and start with the radiator that heated up the fastest. This radiator is usually the one closest to the boiler.
  • Close the lockshield valve fully and then reopen by 1 quarter turn.
  • Using your thermometer, measure the temperature of the pipe directly below the lockshield valve. Next, measure the temperature of the pipe directly below the TRV or manual valve at the other end.
  • If the difference is 12°c, you are extremely lucky and you will not have to make any adjustments, if not – you will need to make minor adjustments to the lockshield valve until the difference reaches 12°c.

Note: It may take a minute or 2 for the adjustments to have a noticeable effect on the pipe temperature so be patient.

Step 6 – Repeat Step 5 for All Other Radiators

Step 6 does exactly what it says on the tin. You will need to repeat step 5 for all of the other radiators in their heating order that you logged earlier. Please bear in mind that the further the radiator from the boiler, the more open the lockshield valve will likely need to be.

Step 7 – Test

Yes, that means, you will have to turn the whole system off again and then repeat the fun bit in Step 4 to make sure all of your radiators are heating up at the same rate.

What to do if your Lockshield Valve is Leaking


As you can see there is a little more to a heating system than just having your lockshield valves fully open or fully closed. The lockshield valve is there to help regulate the water flow meaning that your heating system can work more efficiently and heat the rooms of your house simultaneously at the same rate. A balanced radiator system is an important and often overlooked factor when heating your home. If this has not solved your issue, it may be best to try again and if this is unsuccessful, you will probably need to call a trained professional as there may be another underlying problem at work.

Plumbing Wizard Tips

“Always start with the radiator that has heated up the fastest!”

“Once balanced, test that they are heated at an equal rate by turning them off and then back on again!”

“If this does not solve your issue, call a trained professional!”

“Remember, it is important to open the lockshield valves and also the manual valves or TRVs if you have them!”

Frequently Asked Questions

Why are some of my radiators hotter than others?

It could be a couple of different reasons. Pipes can get blocked and need cleaning or other maintenance work, valves may be in the wrong position for some radiators which leaves the system unbalanced, thermostat placement, and too many radiators nearby.

Does balancing radiators make a difference?

Yes. Radiators need to be balanced on both the supply and return sides to ensure that there are no “hot spots” in the home. Balanced radiators will mean that the home heats up evenly throughout. Hot spots increase the air temperature, which leads to increased energy consumption, poor indoor air quality, high relative humidity levels, and damage to furniture over time (not to mention unhappy customers).

What should the temperature drop across a radiator be?

The temperature drop across a radiator should be 12°c (20°f). This is to ensure the optimum flow which keeps your system working efficiently.

Why are my radiators hot upstairs and lukewarm downstairs?

Quite simply, your radiators are out of balance. Balancing is the technique of regulating the water flow to ensure that your radiators all heat up at the same time and to the same temperature.

It is not too difficult to do and we have a guide above to help you but if you are still unsure, call a professional.

What is radiator balancing and why is it important?

Radiator balancing refers to the process of adjusting the flow of water through each radiator in a heating system to ensure that they all heat up evenly. This is important to ensure efficient and effective heating throughout the entire home.

How do I know if my radiators need balancing?

Signs that your radiators may need balancing include uneven heat distribution, cold spots on radiators, and excessive noise from the heating system.

What tools do I need to balance my radiators?

To balance your radiators, you will need a digital thermometer, radiator key and a set of adjustable pliers.

Can I balance my radiators myself?

If you are handy and have experience with plumbing and heating systems, you may be able to balance your radiators yourself with the proper tools and instructions.

How often do radiators need to be balanced?

Radiators should be balanced at least once a year, or whenever you notice any issues with the heating system.

Are there any risks to balancing radiators?

Balancing radiators is a relatively safe procedure, but it’s important to follow proper safety procedures before working on the heating system – making sure that you do not get burnt etc.

Can balancing my radiators save me money on my heating bill?

Yes, properly balanced radiators can help your heating system run more efficiently, which can help lower your heating costs.

What happens if I don’t balance my radiators?

If your radiators are not balanced, you may experience uneven heat distribution, cold spots, and increased noise from the heating system. This can also lead to higher heating costs and potential damage to your heating system.


Lee Pearce is not just a master plumber; he’s a veritable Plumbing Wizard. With over 30 years of experience in the trenches of pipes and drains, Lee has become the go-to sage for DIY plumbing, saving homeowners thousands in potential call-out charges. As the founder of Plumbing Wizard, he’s dedicated to demystifying the complexities of home plumbing, offering easy-to-follow advice that stands the test of time and pressure. His online blog is a treasure trove of tips, tricks, and tutorials that empower everyday individuals to take charge of their home’s plumbing health. Lee’s practical wisdom is not just about fixing leaks; it’s about imparting confidence and self-reliance. When he’s not writing or elbow-deep in a plumbing project, Lee is passionate about educating the next generation of DIYers, ensuring that practical skills are passed down and preserved.

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