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    What are the 3 types of boilers?

    When picking a boiler, it is important to understand the different types of boilers and which boiler is the right choice for your home. There are 3 main types of boilers: 

    • Combi Boiler
    • Heat Only Boiler 
    • System Boiler 

    Whether you are replacing your current boiler due to its age or needing a boiler system that can meet your demands you should always understand what makes each boiler different before deciding. if you choose a boiler bigger than your needs you could see an increase in bills due to the increase of energy that you may not need nor afford. 

    Heat only Boiler 

    What is a heat-only boiler? 

    Heat-only boilers, also referred to as open vent system boilers, or regular conventional boilers, are usually found in properties that are large or require a higher demand for hot water need to multiple bathrooms or for two or more showers at the same time.  

    A heat-only boiler uses numerous controls to distribute hot water throughout the home including valves, pumps, and tanks. Compared to a Combi boiler, heat-only boilers are bulky and require a hot water cylinder, cold water tank (usually stored in the loft), pumps to circulate the water, and an expansion tank maintains the levels of water needed for the heating system. 

    If you require the need for multiple taps or bathroom facilities to be used at the same time or your home is large in size with a number of people living in the home then a heat-only boiler would be beneficial for your home. We stock a range of heat only boiler parts including baxi heat-only boiler parts which means if your boiler ever has an issue you will be able to easily replace the required boiler part instead of replacing the whole system. 


    System Boiler  

    What is a system boiler? 

    System Boilers are very similar to Heat Only Boilers however there is a big difference between how both boilers function. System Boilers also require external systems and controls such as a water cylinder for storage however, they differ from a regular boiler as the system boilers system uses a pressurised heating circuit which is topped up by mains water, unlike a heat-only system which uses a feed and expansion tank. 

    A System boiler can deliver a high volume of heated water to multiple taps just like a heat-only system however, a system boiler can utilise the water supply from the mains directly without requiring a cold water tank, making it a more compact system than a heat-only system.  

    Combi boilers provide hot water on demand, whereas, systems boilers have a cylinder to provide hot water for later use. If you only have one bathroom you may opt for a combi boiler but if you have multiple bathrooms and a large household you should opt for a system boiler as system boilers have the capacity to store water for a period of time, allowing the system to easily manage numerous heated water facilities and functions at once in including radiators and taps. We supply a range of boiler parts for systems boilers including Vaillant system boilers and Ideal boiler systems. 

    Top Energy Saving Tips 2022

    Saving energy is not only good for the environment – it can also be great for your wallet. By making a few simple changes in your home, you can significantly reduce your energy consumption and save money on your utility bills. 

    Here are 15 top tips to help you save energy and reduce your carbon footprint: 

    1. Get a smart thermostat

    A smart thermostat is one of the best ways to save energy and lower your heating and cooling costs. Smart thermostats can automatically adjust the temperature in your home based on your daily schedule, saving you money on your energy bill. 

    1. Seal drafts

    One of the biggest sources of wasted energy in homes is drafts. By sealing up any cracks or gaps around doors and windows, you can prevent heat from escaping your home, making it more comfortable and saving you money on your energy bill. 

    1. Insulate your home

    Insulating your home is one of the most effective ways to save energy and keep your home comfortable. By properly insulating your walls, floors, and ceilings, you can reduce heat loss in your home and save money on your energy bill. 

    1. Use energy-efficient light bulbs

    One of the easiest ways to save energy is to switch to energy-efficient light bulbs. Energy-efficient light bulbs use less electricity than traditional incandescent bulbs, so they’ll save you money on your energy bill. 

    1. Turn off lights when you leave the room

    One of the simplest ways to save energy is to turn off lights when you’re not using them. When you leave a room, make sure to turn off the lights to save energy and lower your electricity bill. 

    1. Use a power strip

    An easy way to save energy is to plug all your electronics into a power strip and then turn off the power strip when you’re not using them. This will prevent your electronics from wasting energy by staying plugged in and turned on when you’re not using them. 

    1. Unplug chargers when you’re not using them

    Most people don’t realize that their chargers continue to use electricity even when they’re not plugged into an electronic device. To save energy, make sure to unplug your chargers when you’re not using them. 

    1. Use a programmable thermostat

    A programmable thermostat can help you save energy by automatically adjusting the temperature in your home based on your daily schedule. By setting your thermostat to a lower temperature when you’re away from home, you can save money on your energy bill. 

    1. Reduce water heater temperature

    One way to save energy and lower your utility bills is to reduce the temperature of your water heater. Most water heaters are set to 140 degrees Fahrenheit, but you can save energy by turning it down to 120 degrees. 

    1. Educate your family and friends about energy saving

    One of the best ways to save energy is to educate your family and friends about it. By raising awareness about energy saving, you can encourage others to make small changes in their own lives that will collectively have a big impact. 

    1. Bring your own shopping bags

    Say no to plastic bags and bring your own reusable shopping bags instead. This will help reduce the amount of waste produced by plastic bags, as well as save energy and resources used to produce them. 

    1. Use recycled paper

    Using recycled paper is a great way to save energy and resources. Recycled paper uses less energy and water to produce, so it’s more environmentally friendly than traditional paper. 

    1. Reduce, reuse, recycle

    One of the best ways to save energy is to reduce, reuse, and recycle. By reducing the amount of waste you produce, you can save energy and resources used to produce new products. And by reusing and recycling materials, you can further reduce your impact on the environment. 

    1. Compost food scraps

    Composting is a great way to reduce the amount of waste you produce and save energy. Food scraps that are thrown away decompose and release methane gas, which is a greenhouse gas that contributes to climate change. But when you compost food scraps, they decompose into nutrient-rich soil that can be used to grow new plants. 

    1. Save energy with solar power

    Solar power is a renewable energy source that can help you save money on your energy bill. Solar panels convert the sun’s energy into electricity, which can be used to power your home. And since solar power is renewable, it’s a sustainable way to reduce your carbon footprint. 

    In Closing 

    These are just a few of the many ways you can save energy and lower your utility bills. By making small changes in your daily routine, you can have a big impact on the environment. So start saving energy today! 

    How to repressurise a Worcester boiler

    If your boiler isn’t working as it should be, or you’re left without heating and/or hot water, you may need to repressurise the system. Thankfully you shouldn’t need to call in an engineer as this is a fairly quick and easy job that you can do yourself. However, Worcester Bosch boilers are repressurised in a slightly different way to other types of modern combi boilers. So, it is important that you know exactly what to do to repressurise your boiler safely and effectively. 

    How will I know if my boiler pressure is low? 

    The first indicator that your Worcester boiler pressure is low will be if your central heating or hot water isn’t functioning properly. To find out for sure though, you should check the water pressure gauge on the front of your boiler. This gauge will either be in the form of a hydraulic dial or a digital reading. Normally, your gauge should sit between 1 and 1.5, but if it’s reading less than 1 bar, your boiler pressure is too low and requires repressurising. 

    What causes boiler pressure to drop? 

    There are two main causes when it comes to your boiler losing pressure. Firstly, any leaks in the system can result in a loss of water pressure, so be sure to check around your pipes, radiators, and boiler for any sign of a leak or damp areas. Remember to never look inside your boiler yourself though, only a Gas Safe engineer should do this. If you do find a leak around any part of your heating system, contact an engineer as soon as possible to help. 

    Also, bleeding your radiators can sometimes cause a loss of boiler pressure, so you should repressurise it each time after you bleed your radiators. 

    How to repressurise your Worcester boiler 

    Repressurising your boiler simply means to allow more water to enter the system. A lot of other combi boilers use a filling loop to achieve this, but some Worcester boilers use an internal filling key. Before you repressurise your boiler, don’t forget to turn off your electrics and double check the manufacturer’s booklet to ensure everything goes smoothly. 

    • Take off the hatch on the underneath of your boiler, you will find the internal Worcester filling key clipped inside. 
    • Find the filling link in the newly opened boiler. This is a small hole slightly to the right of a white square in which the key will slot into. 
    • Firmly push the Worcester boiler key into the filling link until the arrow on the side of the key nearly touches the black plastic. 
    • Rotate the key anticlockwise until the arrow is facing towards you. 
    • Carefully turn the white square clockwise to enable cold mains water to enter the system. You will probably hear this. 
    • Wait for the pressure to get between 1 and 1.5 on the pressure gauge. 
    • When it has, rotate the square back to its original position and turn off the water. 
    • Place an old towel under the boiler to catch any water spills before turning the filling key back around and removing it from the boiler. 
    • Dry off the key and put it back in the tray and then put the hatch of the boiler back into place. 
    • Turn the boiler back on and press the reset button if needed. 


    Contact National Boiler Spares today if you need help finding the right parts for your boiler. 


    How To Repressurise A Boiler?​

    If you have a boiler at home, then it is important to know how to repressurise it. This is because the boiler can lose pressure, and this can cause a number of problems. 

    Reasons Why Your Boiler Pressure Keeps Dropping 

    A number of things can cause your boiler pressure to drop. The most common reason is that there is a leak in the system. This can be caused by a number of things, such as a faulty valve or a problem with the pipes. 

    Another reason why your boiler pressure might drop is that the system has not been used for a while. This can cause the water to evaporate, and this will lead to a drop in pressure. 

    How To Repressurise A Boiler 

    If you have noticed that your boiler pressure has dropped, then you will need to follow these steps in order to repressurise it: 

    1) Check the pressure gauge 

    The first thing you need to do is check the pressure gauge on your boiler. If the needle is below 1, then this means that your boiler is losing pressure. 

    2) Find the filling loop 

    The next thing you need to do is find the filling loop. This is usually located under the boiler or behind it. 

    3) Turn off the water supply 

    Once you have found the filling loop, you need to turn off the water supply. This is usually done by turning a knob or lever to the “off” position. 

    4) Attach the filling loop to the tap 

    After you have turned off the water supply, you can now attach the filling loop to the tap. Make sure that you do this tightly so that there are no leaks. 

    5) Open the valve on the filling loop 

    Once you have attached the filling loop to the tap, you need to open the valve. This is usually done by turning a knob or lever to the “on” position. 

    6) Check for leaks 

    Once you have opened the valve, you need to check for leaks. If there are any leaks, then you need to turn off the valve and tighten the connection. 

    7) Turn on the water supply 

    After you have checked for leaks, you can now turn on the water supply. This is usually done by turning a knob or lever to the “on” position. 

    8) Check the pressure gauge 

    Once you have turned on the water supply, you need to check the pressure gauge. The needle should now be in the green zone. If it is not, then you may need to repeat steps 2-8. 

    9) Bleed the radiator 

    Once the pressure gauge is in the green zone, you need to bleed the radiator. This is done by opening the bleeder valve and letting the water out until it runs clear. 

    10) Close the bleeder valve 

    After the radiator has been bled, you need to close the bleeder valve. This is usually done by turning a knob or lever to the “off” position. 

    These are the ten simple steps on how to repressurise your boiler. By following these steps, you can ensure that your boiler is working properly and efficiently. 

    How To Reduce Boiler Pressure 

    If your boiler pressure is too high, then you can follow these quick and easy steps to reduce it. 

    1) Check the pressure gauge 

    The first thing you need to do is check the pressure gauge on your boiler. If the needle is in the red zone, then this means that your boiler pressure is too high. 

    2) Find the release valve 

    The next thing you need to do is find the release valve. This is usually located under the boiler or behind it. 

    3) Turn the valve to the “release” position 

    Once you have found the release valve, you need to turn it to the “release” position. This is usually done by turning a knob or lever to the “release” position. 

    4) Check the pressure gauge 

    Once you have turned the release valve, you need to check the pressure gauge. The needle should now be in the green zone. If it is not, then you may need to repeat steps 2-4. 

    Boiler pressure can be too high or too low, and this can be caused by a variety of different things. If you have noticed that your boiler pressure has dropped or risen, then you can follow the steps above to repressurise or reduce it. By following these steps, you can ensure that your boiler is working properly and efficiently. 

    When To Call Professionals 

    If you have followed the steps on how to repressurise your boiler and the pressure is still not in the green zone, then you should call a professional. They will be able to diagnose the problem and fix it so that your boiler is working properly again. 

    How does an expansion vessel work?

    You might not have heard of a boiler expansion vessel before, it’s an essential part of your heating system that helps it to maintain a constant pressure. If you have a closed-water heating system, like a combi boiler, in your home, you will have an expansion vessel. It essentially acts as a sort of shock absorber, dealing with the expansion and contraction of water in your central heating system as it warms up and cools down. 

    If this part stops working, the pressure in your heating system will change too much, meaning your boiler won’t work as it should. This might leave you without heating and hot water until the issue is resolved. In this guide, we will be looking at how expansion vessels work and how you can repressurise them to ensure they’re in full working order. 

    How does an expansion vessel work? 

    The first thing to note about expansion vessels is that they contain both air and water. One side is filled with water from the central heating system and the other with gas (normally nitrogen). This is a requirement in a lot of closed-water systems as water expands as it heats up. 

    If the additional volume of water had nowhere to go, the pressure could increase to high levels, which would cause the pressure relief valve to open. The expansion vessel provides the extra hot water with pretty much an overflow tank, that can help bring the pressure back down to a normal level. Functioning as a spring, the air within the vessel compresses and absorbs the extra pressure, working to keep the system stable. 

    There are several different designs for expansion tanks, but most new boiler systems have bladder style vessels. So, in these systems, the water from the central heating and the compressed air are separated by a flexible membrane (or diaphragm). The vessel includes a Schrader valve on the air side that enables more air to be pumped in when needed in order to maintain appropriate resistance to the expansion of the water. 

    Where is the expansion vessel on a combi boiler? 

    Where your expansion vessel is located will depend on the type and model of boiler you have. In combi boilers, these tanks are often installed within the casing of the appliance itself, so a lot of people aren’t even aware that these components exist. If you’re unsure where the tank is in your heating system, you’ll probably be able to find out in your boiler’s user manual. 

    Remember, only a Gas Safe registered engineer is allowed to take off the casing on a gas appliance. This is the law, so never try to do it yourself. 

    What size expansion vessel do you need? 

    When water is heated up, it can expand to between 4% and 9% of its initial volume. This means that if an expansion vessel is too small it might not be able to do its job properly and won’t take enough water out of the system to reduce the pressure. 

    When you purchase a new boiler, you won’t need to worry about this because it will normally come with an expansion vessel that is suitably sized. If you need to buy a replacement because your boiler expansion vessel has a fault, National Boiler Spares can advise you on the right model for your specific boiler. 

    How to fit an expansion vessel 

    Installing a new expansion vessel can be a challenging and time-consuming task, especially if it isn’t easy to access because of how your boiler is set up. This is definitely not a job you should try to do yourself, only heating engineers should remove and replace these parts. 

    Depending on where it is located, more complicated elements of your boiler might need to be taken out to allow access to the vessel. In certain cases, the boiler will need to be taken off the wall so a new expansion tank can be fitted, which involves disconnecting the flue. 

    What pressure should an expansion vessel be set to? 

    To properly do its job, the compressed air in an expansion vessel needs to be at a suitable pressure. Your boiler manual should inform you how to work out this pressure, but in residential systems this is typically around one bar. 

    You should hear air escaping when you push down on the Schrader valve to check the pressure in the vessel. If you don’t, then there isn’t any pressure. Another indication that something is wrong with the central heating part is if water escapes when you push on the valve. 

    Draining and recharging the vessel should always be tried before contacting the manufacturer for a suspected failed vessel. If this doesn’t work though, it might be that the diaphragm inside has failed, which means you may need to get a new vessel. 

    Contact National Boiler Spares today or explore our product range to see the boiler expansion vessel replacement cost UK. 


    How do I know if my boiler diverter valve is faulty?

    Problems with a boiler diverter valve are common in older types of combi boilers. This is because over time a diverter valve can experience wear and tear of break completely, causing mayhem on central heating systems. Fixing a diverter valve boiler can be simple, but potentially costly. In this guide, we’ll look at the main symptoms of diverter valve faults and give you an idea of what is needed to repair them. 

    Firstly, what is a diverter valve? 

    The purpose of a diverter valve on a combi boiler is similar to that of a lock on a canal – it opens and closes to control domestic hot water (water from taps and showers) and the water that is used to warm up towel rails and radiators. The priority of the diverter valve should always be your domestic hot water over your heating system. 

    In other words, when you turn on a tap, the diverter valve will shut off the heating supply until you’ve turned the tap off. Given that the diverter valve is a mechanism and moving part of your boiler, a lot of the issues with them often comes from the valve sticking. 

    Where is the diverter valve on a combi boiler? 

    If you’re wondering where the diverter valve is on your boiler, it is part of the tub spout. The diverter handle pulls straight up to send all the water from the tub spout to the shower heads or radiators etc. 

    How will you know if your diverter valve is having problems? 

    Lukewarm hot water (taps and showers) 

    Lukewarm water in your taps and showers is one of the most common signs of boiler diverter valve fault. Since the boiler is designed to prioritise hot water, a valve that’s even slightly stuck open on the heating side will enable some of the heat, that’s normally supplied to domestic uses, to escape. 

    You need to leave the heating on to get hot water 

    If it’s a hotter time of year when you don’t normally have your heating on, try switching it on and letting it warm up. If the temperature of the water increases after you’ve turned on the heating, this is likely another common symptom of a diverter valve problem. 

    Lots of water, but no heating 

    This is a common problem relating to diverter valves. If you’re experiencing this, it’s probably the case that your valve is stuck on the hot water side. Even though having hot water is the main priority, the valve is unable to open and let the radiators warm up at all, which is particularly problematic in the winter months. 

    Find any boiler parts you need for an affordable price at National Boiler Spares today. Our team are on hand to help make sure you get the right parts for your boiler to both save you money and ensure you’re getting high quality components that are built to last. 

    Can a diverter valve be repaired?

    When something goes wrong with your combi boiler there is always the fear of how much it will cost to fix. Some boiler issues can be repaired to get the boiler up and running again. However, in some cases the part that is causing the problems can’t be repaired and can only be replaced.  

    Even if that is the outcome for your boiler, replacing elements doesn’t always break the bank. In this article we’ll be breaking down the costs to fix or replace your boiler diverter valve. 

    Repairing a broken diverter valve 

    It is never advisable to try and do a boiler repair yourself, instead you should contact a Gas Safe registered engineer. They will be able to carry out a fault check to make sure a faulty diverter drive is the issue and not something else. 

    There are other boiler problems that can display similar symptoms to a broken diverter. For example, if you’re in a newly built home, or the issue has always been there since you moved in, it could be something as easy as valves on the pipework not being open. 

    The fault check done by the boiler engineer will typically include seeing that all controls are working as they should be. If there’s a fault with your diverter valve, the engineer will probably need to do a diverter valve replacement. 

    In a lot of cases, it will only be the diaphragm that needs to be replaced, but the labour costs involved often make it more worthwhile to get an entirely new unit. It would be much more frustrating if you replaced the diaphragm and then had to call the engineer back shortly after because the valve itself is sticking. 

    Whilst the boiler is taken apart, it is certainly worth asking the engineer to assess other visible parts for wear and tear. If there aren’t any significant issues, then replacing the problematic diverter is all that will be needed. 

    How much does it cost to fix a faulty diverter valve? 

    When it comes to the cost to replace a diverter valve UK, you can expect to pay around £250-£350, but as with all the other parts of a heating system, there’s a lot of factors that influences the cost. Mainly these are the cost of the part itself and the labour costs. 

    Cost of the diverter valve 

    With occasional fluctuations, the average cost of a diverter valve is about £80-£200. If your boiler diverter valve costs £80-£120, £250 should cover the full cost of the repair (including labour). However, if your diverter sits in the £150-£200 region, it’s more likely to cost between £275 and £350 to repair (including labour). 

    Labour costs 

    Hourly rates for labour vary widely across the country. Being in a less expensive area of the UK, compared with London for example, could make £50-£60 difference to the overall cost of repairs. 

    Also, it’s important to keep in mind the ease of replacement. Some broken diverter valves will be easier to get to and replace than others. The quicker and easier it is to replace the part, the less expensive it will be. 

    When shouldn’t you replace a diverter valve? 

    Boilers aged between 8 and 10 years won’t be as advanced as new boilers, and many already have diverter problems at that age. It is recommended that your engineer checks the rest of the boiler parts thoroughly to look for any other issues. If there are any other major faults or issues found, it’s worth thinking about a new boiler. 


    Contact National Boiler Spares today to find a high quality, replacement diverter valve for your boiler today.