Your Most Commonly Asked Radiator Questions

We’ve noticed that there are some questions we get asked more often than others. Below we take a look at a few of these questions that we receive at Radiators Direct to try and give you a little more heating help when you need it!

Q. Why Are Some Radiators Cold While Others Are Hot?

A. If some radiators are cold while others are hot, it’s often due to uneven water flow in the heating system. This can happen if:

1. Trapped Air: Radiators with trapped air won’t heat properly and may need bleeding.

2. Balancing Issues: Incorrect valve settings can cause uneven distribution of hot water.

3. Sludge Buildup: Sludge or debris in the system can block water flow to certain radiators.

Bleeding and balancing your radiators, or performing a system flush, can resolve most issues.

Q. What Is the Best Temperature for Radiators?

A. According to the Energy Saving Trust, you should set your thermostat to the lowest comfortable temperature for your needs. For most people, this is between 18°C and 21°C. If you can, turning down your thermostat from 22°C to 21°C can save £90 a year in GB and £100 in NI on energy bills. Adjust settings based on personal comfort, room size, and insulation quality to maintain efficiency and reduce energy bills.

Q. Why Do Radiators Make a Gurgling or Banging Noise?

A. Radiators make gurgling or banging noises due to air trapped in the system or issues with water flow. Gurgling often occurs when air bubbles disrupt water circulation, which can be fixed by bleeding the radiator. Banging sounds are typically caused by expanding metal, loose pipes, or water hammer, which happens when water flow suddenly stops due to pressure changes. Incorrect pipe installation or blockages can also contribute. Regular maintenance, proper pipe support, and bleeding the system can help eliminate these noises and ensure efficient radiator performance.

Q. Are Radiator sizes Standard?

A. Radiators come in a variety of sizes, but there’s no universal "standard" size. Whilst many horizontal radiators tend to be 500 mm or 600 mm high, and vertical radiators are usually 1600 mm or 1800 mm high, manufacturers offer a wide range to suit different spaces and heating needs. Common widths and heights are designed to fit most homes, but variations exist to accommodate unique layouts, such as compact models for small rooms or tall, slim designs for narrow spaces. When replacing a radiator, it’s best to measure your current one and consider factors like heat output (measured in BTUs) and available wall space to find the perfect fit for your home.

Q. How Often Should I Bleed My Radiators?

A. It is generally good practice to bleed your radiators at least once a year, ideally before the heating season starts in autumn and the cold sets in. This ensures they work efficiently when needed most. Additionally, bleed your radiators whenever you notice cold spots, uneven heating, or gurgling noises, as these are signs of trapped air. Regular bleeding improves heat distribution and reduces strain on your boiler, saving energy and costs. However, over-bleeding can lower system pressure, so always check the pressure gauge on your boiler after bleeding and top up if necessary.

Q. What Does BTU & Delta T Mean?

A. Two important factors that need consideration when it comes to purchasing radiators online (or in a showroom).

Put simply:

BTU (British Thermal Unit) is basically a measurement of thermal energy. It’s used to work out how much heat a room needs in order to maintain a desired temperature. A radiator's BTU rating indicates how well it will heat a room. A higher BTU rating means the radiator has a higher heat output, and can heat a room more quickly or warm a larger space in the same amount of time. Determining the BTU required for a particular room will help you in choosing the radiator(s) right for you. Our online BTU Calculator makes life a little easier and will calculate the BTU requirement your room has based on the details you provide.

Delta T (ΔT) represents the temperature difference between the radiator and the room. It's calculated as the radiator's average water temperature minus the room temperature. Standard ΔT values (e.g., ΔT50°C in Europe) help manufacturers rate radiator performance under consistent conditions. We go into detail about Delta T here on our site and include a handy Delta T Conversion tool.

Q. Would These Radiators Be Powerful Enough to Heat My Room?

A. The power of your radiator depends on the size of your room and its insulation. Radiator power is measured in British Thermal Units (BTUs). To calculate the required BTUs, consider the room’s dimensions, ceiling height, window size, and exposure to external walls. Generally, a small bedroom needs 2,000–3,000 BTUs, while a large living room may require 8,000–12,000 BTUs. Our Online BTU calculator can help with working out how powerful your radiator(s) need to be. Choosing the correct radiator ensures efficient heating without wasting energy.

Q. Can I Paint My Radiator?

A. Whilst our radiators are supplied already painted or finished, you can paint your existing radiators if they are in need of freshening up. Still, it’s important to use heat-resistant radiator paint designed to cope with large temperature changes - standard paints such as regular wall emulsion can peel or discolour due to high temperatures. Start by turning off the radiator and ensuring it’s cold. Clean and sand the surface to remove old paint and rust and to provide a key to improve paint adhesion. Apply a metal or specialist radiator primer first, then use radiator paint in your desired colour. Choose a paint labelled as heat-resistant or specifically designed for radiators. This ensures a durable, attractive finish that withstands heat.

Q. My Radiator Is Leaking, What Do I Do?

A. Leaking radiators can be both frustrating and harmful to your home, but what many don’t realize is that the problem can often be fixed quickly and at minimal cost. First and foremost, stay calm! To avoid a mess, place some old towels underneath the leak to catch and soak up any water, this will buy you time to assess the situation and figure out the best solution. Check out our blog where we go into detail as to what you should do in the event of finding a leaking radiator.

Q. Should Radiators Be Placed Under Windows?

A. Radiators are often placed under windows because they help counteract the cold air entering through the glass. As the radiator emits heat, it creates a convection current that warms the cooler air, improving overall room temperature. This placement is especially effective in older homes with single glazing. However, modern homes with well-insulated double-glazed windows may not require this traditional placement. If furniture or heavy curtains block the radiator, it can reduce heating efficiency, so consider alternative placements in such cases.

Q. Can Radiators Leak Carbon Monoxide?

A. No, radiators themselves do not leak carbon monoxide. However, boilers that supply heat to radiators can emit carbon monoxide if not properly maintained - regular boiler servicing is essential.

Q. Do I Need Valves to Go With My New Radiators?

A. Yes, you do! Choose from a range of contemporary and traditional, manual and Thermostatic Radiator Valves (TRV) in a range of finishes to complement your designer radiator.  To complete the overall look why not include a set of matching pipe covers and shrouds to match the finish of your valve and hide that unsightly pipework? Click here to check out our full range of valves & accessories.

Q. How Can I Make My Radiators More Efficient?

A. To make your radiators more efficient, start by bleeding them to remove trapped air, which can block heat. Next, ensure they’re not obstructed by furniture or curtains, as this limits heat circulation. Regularly clean them to avoid dust buildup, which can reduce efficiency. If possible, install a smart thermostat or thermostatic radiator valves (TRVs) for better temperature control. Lastly, consider insulating pipes and ensuring your boiler is serviced annually for optimal performance.

Q. Is It Safe to Dry Clothes on Radiators?

A. Drying clothes on radiators is not recommended. It reduces heating efficiency, increases humidity, and can cause condensation and mould. Use a heated airer or standard airer instead for better results. We addressed this question in great detail in our latest blog article.