Add radiator to existing system: Cast Iron Radiators | How to Fit a New Radiator | New Radiator

Adding radiators to an existing system

During the cold winter months, it’s particularly important to be able to heat your home comfortably to maintain a certain standard of living conditions. You may have a room in your home that always feels quite cold and could do with an additional radiator being installed. Alternatively, you might have a room that has no central heating in it at all, making it somewhere you can’t really use for much of the year. In this article, we’ll look at some factors to consider before deciding whether to connect extra radiators to an existing central heating system.

Is your boiler powerful enough?

It’s all very well wanting to add extra radiators into your home, but a very important point to check is whether your boiler actually has the capacity to cope with additional radiators.

When your existing boiler was installed, the plumber or heating engineer would have selected a boiler in accordance with the size of your house and the amount of radiators on the system. Putting in one or two extra radiators will probably be fine, though you should always check the capacity of your boiler in the manufacturer’s manual before proceeding. If you wanted multiple extra radiators, it’s very likely you’ll need to upgrade your boiler as well.

If you haven’t had your boiler serviced for a long time, it’s worth getting in a heating engineer to give it an ‘MOT’. You might find this improves the efficiency of your boiler and negates the need for additional rads.

Are your current radiators working properly?

Through years and years of use, radiators can start to develop problems and emit less heat than they did when they were new. Inefficient radiators can also cause boilers to work harder, using more energy to heat your home and resulting in higher gas bills.

A very common problem is radiator sludge. This is caused by corrosion inside your radiators, with tiny shards of rust breaking off and settling into a brown sludge at the bottom of your radiators. Over time, this can cause your radiator to feel hot at the top, but cool (or even cold) at the bottom. Your room won’t be heating up very efficiently and you might find the room struggling to stay at a comfortable temperature. Having your radiators power-flushed, or even replacing your old radiators with new ones, may increase the heat in your home and help keep your gas bills from being unnecessarily high.

Are your current radiators large enough?

In decades gone by, the limitations of radiator design often meant that many homes contained radiators that were not really large enough to adequately heat the rooms they were installed in. If you have an old central heating system that hasn’t been updated for many years, you may have some radiators like this – typically small, single panel convector radiators positioned in odd places in a room.

Radiator manufacturing has made huge strides in recent years with double panels, double rows of convector fins and vertically-orientated radiators all being very popular ways of increasing the heat outputs with minimal disruption. In many cases it’s perfectly possible to replace an old radiator with a modern one capable of emitting far more heat without the need for replacing or moving existing pipework.

A helpful tip is to use a heating calculator to establish how much heat (in BTUs) you need to heat a room and then set about finding a radiator that emits that amount of heat. You could measure the distance between the two pipes on your existing radiator (the ‘Pipe Centres’ measurement) and also look for a radiator with the same measurements. This would help you find a radiator that will comfortably heat your room and slot directly onto your existing pipes without any disruption.

Installing a new radiator

If you think that adding a new radiator is the right course of action for you and you have found a radiator that doesn’t require any alterations to existing pipework, then this is a task you can have a go at yourself.

If you can’t use existing pipework or your chosen room has no hot water pipes at all, this is a job for a more experienced DIYer or a professional. Pulling up floorboards and laying or re-routing water pipes is an in-depth job and not something to be tackled if you’re not confident in your DIY skills. If in doubt, call in a pro!

In the video below, you’ll see a professional plumber showing you step-by-step how to install a radiator onto some already existing pipework. You’ll note the importance of draining down the system first to ensure that no water spills out onto the floor.

In the video below, you’ll see a professional plumber adding pipes to a radiator in a situation where previous pipes were not suitable for the new radiator.

Huge range at Trade Radiators

If you are looking for an extra radiator to add to your existing central heating system, then we’ve got a massive variety to choose from at Trade Radiators.

At Trade Radiators we want everyone to find the ideal radiator for any space, whether you’re looking for a no-fuss simple heating solution to the box bedroom upstairs, or fancy updating your old bathroom panel radiator for a sleek new chrome towel rail.

With the best range of radiators you’ll find from any UK store, better delivery and our unique price promise, we aim to help any room across the country get the radiator it deserves. It all starts with knowing what you need from a new radiator. Shop our extensive range of quality radiators by what matters to you most. Whether you’re looking for a specific style of radiator, such as column or designer, or a particular colour to suit your home’s interior, Trade Radiators has something to suit you.


How to Add a Radiator

When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.

The problem with radiators is there are never enough of them to go round and often they’re the wrong place. The quickest and easiest way to upgrade your central heating system is by adding a radiator – but why pay someone to do it when you can follow our easy step-by-step guide and do it yourself in a day?

Our step-by-step guide shows you how to upgrade your heating system in a day.

Adding a radiator is a straightforward but time-consuming business, that’s why a plumber will charge you around £100 a radiator, plus materials, to fit one for you. If you have solid floors or need a particularly long run of pipes installed, you can keep on adding to that figure.

We’ve put together this handy guide to adding a radiator to your central heating system. The guide covers the most popular form of wet central heating: the open-vented system that uses flow and return pipes to distribute hot water from the boiler to the radiators and back to the boiler.

(MORE: See more DIY tutorials)

Tools needed

  • Butane torch
  • Pipe cutter
  • Adjustable spanner
  • Radiator valve key
  • Bleed valve key
  • Paint pen,
  • Tape measure
  • Drill and drill bits
  • Pencil
  • Screwdrivers,
  • Flameproof mat
  • Plastic hose/pipe cutter

Materials needed

  • Pre-soldered 15mm bends, tees and straight connectors
  • or Plastic quickfit 15mm bends, tees, straight connectors
  • 15mm copper pipe
  • or 5mm plastic pipe
  • Radiator
  • Radiator valves
  • Flux
  • Butane
  • Spare 15mm olives
  • PTFE tape
  • Pipe clips
  • Screws
  • Rawlplugs

Think carefully about where you are going to position your new radiator. Is one part of the room particularly cold? Will its benefits be negated by any future furniture moves? Also think about the rooms overall heating needs: this is measured in British Thermal Units (BTU) and most radiators have a sticker on them showing the BTU output. To work out how many BTU your room needs multiply the height by the width and length of the room (in feet) and then multiply this figure by four.

How many extra radiators can your boiler take? When a boiler is fitted the plumber takes into account the size of the house and fits a boiler with an appropriate BTU capacity. Normally, adding one or two radiators shouldnt cause any problems but its a good idea to check the boilers output (in the instruction manual or available from the manufacturer) and have an idea of the demands placed on the boiler by the existing radiators.

1. Once you’ve established where you are going to position the radiator, find the nearest pair of flow and return pipes that you can connect into. These can be positioned under floorboards or, as here, attached to a wall because of the solid ground floor.With the central heating system cold, turn the thermostat until it clicks and then touch both pipes. The pipe that gets hot first is the flow pipe from the boiler. Mark the flow and return pipes clearly with a paint pen.

2. Turn the boiler off and make sure that the water supply to the unit is turned off too. Attach a length of garden hose to the draincock on the radiator and run the hose to a point outside thats lower than the radiator. Undo the square key underneath the draincock and let the system drain down.

3. Releasing air from the radiator bleed valves lets air into the top of the radiator and forces out any water left in the system. Remember to do the valves up afterwards.

4. Find the centre point of the wall and draw a vertical pencil line at this point. Find the centre line of the radiator and then measure out from this point to the centre of the brackets. Transfer these measurements to the wall.

5. Some radiators come with a template for marking off the bracket hole positions. Offer this up to the lines already drawn and spot through with a pencil. If theres no template, slot the bracket onto the back of the radiator and measure from the base of the bracket to at least 50mm below the bottom of the radiator (some radiator manufacturers recommend up to 125mm clearance check packaging for details). Starting from the top of the skirting board, transfer this measurement onto the wall. If the system has drained down, you can now do up the draincock.

6. Put the base of the bracket on the line drawn in step 5 and then mark off the brackets top hole on the wall. Drill and rawlplug the wall, loosely attach the brackets at the top and then mark off and drill the bottom holes.

7. Wrap PTFE tape around the threaded parts of the radiator valves five times. This helps them to seal.

8.  Fit the valves. Do up the main body of the valve with the correct hexagonal key thats available from DIY stores. Use an adjustable spanner to tighten the outer part of the valve onto the main body.

9. Hang the radiator.

10. Cut and fabricate the pipework required from the radiator back to the flow and return pipes you identified earlier. If youre working with copper pipe use a proper pipe cutter never a hacksaw. Mark out where you intend to fix brackets to support the pipe runs and screw them in place now.

11. If you are using copper pipes check that everything fits together before you start soldering and that no stresses are created when the pipework is attached.

12. Clean the ends of the copper pipes with wire wool.

13. Slide the retaining nuts and olives over the pipes that are connecting to the radiator valves and hold them in place while you tighten them.

14.  For this part of the job were using pre-soldered or Yorkshire joints that just need to be heated evenly with a butane torch to melt the solder inside the joint and make a watertight joint. Use a flameproof mat behind the area being heated to prevent fires and the chance of un-soldering existing joints.

15. You can stop heating a pre-soldered joint when the solder appears in a ring around the edge of the joint like this. Dont forget: both ends of a presoldered joint must be heated at the same time.

16. Once you’ve got the pipework from the new radiator in the area of the pipe you plan to connect into, youll have to cut the pipe and insert a tee piece to take the feed. In this case were using a quick-fit plastic tee to demonstrate how traditional and modern plumbing components can work together.

17. Plastic pipe should be cut with the correct hose/pipe cutter rather than a hacksaw that tends to leave a frayed edge. Make sure the cut is square.

18. Before you connect plastic pipe to a connector, push an insert into the end to stop the pipe deforming in action.

19. Connect up the flow and return pipes to the pipes from the new radiator. If you have fitted a thermostatic valve to one side of your radiator and its not a bi-flow type then the flow feed must be connected to that valve. Refill the system by turning on the tap you turned off in step

20. Check for leaks and then bleed the air out of the radiators.

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how to add radiator sections, extension, connection


Causes of poor heating
How to add sections to the radiator
Preparation of materials and tools
Building – how to build radiators correctly
Additional recommendations

Sometimes it happens that the once efficient heating system ceases to cope with its tasks, which is expressed in poor heating of the home and rapid cooling of the radiators. One of the solutions to this problem is docking additional sections to the batteries.

Causes of poor heating

Basically, the lack of space heating occurs due to errors in the calculation of the number of radiator sections. If there are fewer of them than necessary, heating devices are not able to provide the proper temperature in the house. This situation develops, as a rule, due to the fact that the batteries are installed in a dwelling with a minimum number of sections. As a result, their area is simply not enough for high-quality heating and keeping warm for a long period of time.

How to add sections to the radiator

In order not to start a time-consuming and expensive procedure for the reconstruction of the entire heating system, they usually resort to another option – wind up additional sections. This work is not very difficult, therefore, it is often carried out by the owners of the dwellings themselves. It is important to understand how to connect heating radiators to each other correctly. The main thing is to study the technology well, how to build up heating batteries. This will ensure that the procedure will be performed efficiently and quickly.

Preparation of materials and tools

Before adding sections to a bimetallic radiator, you need to prepare the following materials and tools:

  • Extension section.
  • Special wrench for pipes (gas).
  • Intersection seals for batteries.
  • Heating nipple set.
  • Sandpaper.
  • Key for radiators.
  • Side battery plugs with left and right hand threads.
  • Paronite gaskets.


Before you build up the battery, it must be removed and properly prepared. The device is cleaned of dust and rust, after which an audit is made of the threaded hole intended for switching the battery and the supply pipe. As a rule, over the years of operation, growths form on it due to the increased hardness of the water and the presence of bleach in it.

It is imperative to get rid of these formations. To do this, use sandpaper, processing a threaded hole with it. In this case, special care must be observed, because. even small residues of build-up will prevent the tightness of the installation of gaskets. In the future, this leads to the appearance of leaks along the switching junction.

Extension – how to extend radiators correctly

The connection of sections of bimetallic radiators is carried out in the following sequence of operations:

  1. The removed radiator is placed on a flat base, and an additional section is placed opposite it. It should be taken into account that one of its sides is equipped with a right-hand thread, and the other with a left-hand one. Then you need to take the nipple, positioning it in such a way as to match the threads on the connected sections. Then it is screwed onto the left end of the battery by one thread. Upon completion of the procedure, they do the same with the element for the lower part of the radiator.
  2. After that, the sections prepared for connection are tightly attached to each other. A seal is laid between them, measuring the distance to the nipple (for this you need a radiator key). It is inserted to the measured length into a special niche on the back end of the radiator. In order to scroll the radiator key, a pipe key is used.
  3. When screwing the nipple, it is important to make sure that it sinks into the opposite battery sections at the same time. Upon completion of this procedure, three full turns are made using the radiator key. This helps to ensure that the nipple is fixed as tightly as possible.
  4. In the next step, the radiator key is moved to the other side of the heater. The screwing procedure is carried out in the same order as with the lower part. An important condition: at the end of the process, the switched sections should be as tight as possible.
  5. At the end, side plugs and paronite gaskets are installed on the battery. For these purposes, you will need a pipe wrench. It is important to achieve the strongest possible screwing to create good tightness. This will ensure that water does not seep through at the junction. This is the last operation in building up the battery of the heating system.

Additional recommendations

Installation of cranes is not a mandatory procedure, and is carried out on request. In cases where an increase in the power of the heating device will require installation on one, but several additional sections, the above instructions are used for this. This is also true for working with other types of radiators, since adding a section to aluminum radiators is no different.

The main thing is to follow the given sequence of operations, and not to rush. Connect bimetallic radiators as tightly as possible. This will ensure that everything is done correctly, and the heating of the house will receive the necessary increase.

Connecting a heating radiator to a two-pipe system: analysis of all possible methods

There are several ways to connect a heating radiator to a two-pipe system. The method of supply affects the efficiency of heat transfer of the battery, so the issue of its choice should be given special attention.

In the article, we outlined the pros and cons of a two-pipe heating system, described the specifics of different pipeline connection schemes, and also provided recommendations on choosing the best supply option based on the type of radiator and the characteristics of the room.

Article content:

  • Why is a two-pipe system good?
  • Piping connection points to the battery
  • Radiator connection methods
    • Option #1 – with top wiring
    • Option #2 – with bottom connection
  • Conclusions and useful video on the topic
  • 900 37

    Why is a two-pipe scheme good?

    Existing heating systems are divided into three groups – one-pipe, two-pipe and manifold. The cheapest option to implement is the first option. However, it is the least efficient in terms of the controllability of heat transfer in rooms and the consumption of thermal energy.

    The scheme with . But it will cost the most to create. An analogue with two pipes occupies a certain middle between them in terms of cost and performance.

    A two-pipe system is much more efficient than a one-pipe system, and if properly designed, it costs only 10–25 percent more to install than it. As a result, each battery in the circuit receives almost the same amount of heat to release it into the room.

    In a single-pipe analog, the coolant is supplied to the radiator and discharged through one common heating pipeline. In this case, the first room heater from the boiler (boiler) receives much more heat energy than the last one in the chain. And it turns out that in the room farthest from the water heater it is always cool, and in the room closest to it it is too hot.

    The basic visual difference between these systems is the presence of a bypass in the single-pipe distribution next to the battery. This jumper ensures uninterrupted circulation of the coolant when one of the radiators is required to be completely or partially disconnected from the heating. In a heating circuit with two pipes, it is simply not needed.

    Among the main advantages of using a two-pipe system:

    • the accuracy of heat transfer adjustment for individual rooms;
    • versatility – suitable for all homes;
    • independent operation of individual radiators from others;
    • the ability to quickly install additional batteries.

    Efficiency, however, comes at the cost of increased length. Each radiator in such a system is supplied with a pair of pipelines with a coolant from the boiler – one for the supply of heated water, the second for the return.

    A common mistake when choosing between one-pipe and two-pipe schemes – the second option, according to the estimate, is one and a half to two times more expensive than the first, which is completely wrong. As a result, the total cost of these two options for materials does not differ so much.

    But the volume of installation work is indeed doubling. If the installation is done by hand, then this moment is not so relevant. However, if you order the assembly of the system on the side, then you will have to pay a little more for a scheme with two pipelines. But it certainly won’t cost twice as much.

    Connection points of pipes to the radiator

    Before choosing a method of connecting a radiator to a water heating system, it is necessary to carefully examine the heater itself.

    It consists of a pair of horizontal collectors interconnected by vertical bridges. On top of this entire structure, a “casing” is put on in the form of a heat exchanger with the maximum possible area of ​​​​contact with the air around.

    The classic aluminium, steel, bimetal or cast iron radiator has four pipe connections, but there are also options with only two pipes

    To connect the device in question to any pipe heating system, only an inlet and an outlet are required. Manufacturers make four connection points in the radiator for the sake of versatility. So the battery can be connected in any of the existing ways, simply by closing the two remaining inputs and outputs with plugs.

    Heating pipe connections are located on the side or bottom of the radiator. Lateral connection is more practical and the most common.

    The lower counterpart is usually chosen for aesthetic reasons. With it, pipelines can be mounted in the floor, making them completely invisible. The interior is more beautiful as a result.

    In radiators with pipe connectors from below, there is a special jumper inside, which makes the coolant circulate over the entire area of ​​​​the heater, and not immediately go to the return outlet without heat transfer

    There is no fundamental difference in heat transfer between “side” and “lower” radiators. Here, the method of connecting pipelines with a mutual arrangement relative to each other of the supply and return is more important.

    In this case, devices with pipes from below are recommended to be connected only in systems with, and not. In the second case, it will be too difficult for heated water to rise from the inlet upwards and heat the battery.

    Ways of connecting a radiator

    The efficiency of heat transfer of a radiator directly depends on the choice of the scheme for connecting heating pipelines. If the coolant does not circulate over its entire internal area, but quickly goes into the return line, then the battery gives off heat to a minimum.

    The most efficient connection method is diagonal. With it, the water inside the radiator has time to cover all sections on the way from the inlet to the outlet, giving each of them thermal energy

    There are three ways to bring pipes with coolant to the radiator:

    • lateral one-sided – pipes are located on the side on one side;
    • horizontal – bottom or top – the pipes are at the same level horizontally relative to each other on top or bottom of the battery – one fits on the right and the second on the left;
    • diagonal cross – pipes are connected diagonally.

    In the passports for radiators, heat transfer is usually indicated for a diagonal connection method. With lateral connection, heat loss will reach 10% of this maximum. And with the horizontal version, they can reach all 20-25%.

    However, much here depends on the number of sections and the internal structure of the battery. Plus, an important role is played by the material of manufacture of the radiator, as well as its location in the room.

    See .

    Piping schemes for the supply of coolant are:

    • with top supply;
    • with bottom connection.

    If the system is with natural circulation, then the scheme with the top wiring will be more efficient and preferable. But if available, both options are acceptable.

    Directly on the method of supplying heating pipes does not depend much. Supply and return are connected to the battery in accordance with the selected scheme. And the remaining two holes are closed with a Mayevsky crane and a plug.

    Option #1 – with top wiring

    In this scheme, the coolant line to the radiator comes from above. The outlet pipe can be connected from the same side, in the lateral version, or from the other (diagonal analog). In this case, the movement of water in the supply and return circuits can be passing or counter (dead end).

    If there are less than ten sections in the radiator, then the lateral method of connecting pipes is practically not inferior to the diagonal one – but with more of them, the coolant will reach the edge of the battery farthest from the entrance only with strong pressure in the system

    In this case, the return and supply circuits are approximately the same length, which greatly simplifies the balancing of the entire system.

    The diagonal method of connecting pipes with a top coolant supply is considered the most effective. However, with proper design, other options are also quite applicable. And, often, they also turn out to be more profitable in price. In this case, all work can be done independently.

    In practice, a dead-end scheme is more often used, since it requires slightly less pipes by the footage.

    If the house is small – up to 200 sq. m and you want to save as much as possible on the heating system, you should prefer the scheme with the oncoming movement of heated water. Here, the adjustment is not so complicated and quite realizable. But for a large cottage – two to four floors, it is better to choose something else.

    Option #2 – bottom connection

    In this case, the heating medium is supplied from below. If such a wiring is built in a one-story house, then this allows you to get rid of the risers. Both pipes are laid from the boiler along the floor and do not warp the interior so much. The less pipelines in the room, the more beautiful everything looks.

    The main advantage of the lower supply is the absence of risers, which slightly reduces the amount of the estimate for the arrangement of the heating system in the house

    The return can be connected in such a scheme:

    • on the side;
    • horizontal bottom;
    • diagonal.

    If a conventional radiator is used, without a special baffle for more efficient circulation of the coolant inside, it is best to choose a diagonal connection method.

    However, the hydraulic resistance in this case is greater than with the horizontal version. Here we must carefully consider what is more profitable when doing.

    Often, the horizontal method is the most efficient in terms of heat loss. But this is only possible if there is a plug at the inlet between the first and second sections of the battery, which directs the coolant up the entire radiator. So the resistance is minimal, and the heat transfer is maximum.

    The bottom connection is only recommended for circulating heating systems. With the natural movement of the coolant, air will constantly accumulate in the radiators, especially with horizontal and lateral connection of pipelines.

    It will have to be constantly lowered with . And these are additional body movements, so it is better to initially rid yourself of such worries.