Installing a central heating system

Installing a central heating system will cause considerable domestic upheaval. To reduce this to a minimum, plan as much of the work as possible in advance.

Work systematically, have everything to hand, and complete each stage before starting on the next. This cannot be stressed too much. Try to install everything possible before you cut into the domestic water system.


1. pipe cutters, hacksaw and files

2. Allen keys (to fit radiator blanking plug and air vent)

3. bending springs 15mm and 22mm

4. spanners or Stilson wrench butane blowlamp (can be hired)

5. floorboard bolster and claw hammer (for lifting floorboards)

6. hand brace and bits and a saw

7. spirit level, screws No 12 and wall plugs

8. lead light


1. lead-free solder and flux

2. PTFE tape and non-toxic sealing compound

3. wire wool

4. heat-resistant mat to prevent burning

5. copper fittings

The different kinds of copper fittings fall under two headings: Compression fittings have olives (rings) and nuts. If you have very little experience of copper installation this is the best type of fitting to use as only a small amount of sealing compound and a spanner to tighten the nut are needed, but these fittings are more expensive.

Capillary fittings come in two types. Some have a ring of solder included inside, which are known as integral ring fittings. The others are called end feed fittings to which the solder is added afterwards.

Capillary fittings are neater and cheaper, but need more skill to make good joints.

If a leak does occur with capillary fittings, part or all of the system may have to be drained down because of the presence of water.

All pipework and fittings must conform with British standards.

Buying equipment

Try to work out from your plan and room layout the amount of pipework, bends, and tees that are necessary to connect the equipment, as well as the equipment you will need.

Make a list, go to your supplier and ask for advice on what type of fittings are required. Also ask if you can return any that are not needed, because fittings are expensive.

When buying pipework allow extra, because without doubt you will make some mistakes and there will be offcuts that cannot be used.

Do not try to carry all the equipment in your car; it is heavy and awkward and it is well worth having it delivered.

Level get air locks in them.

Radiators are fixed about 150mm frorr the floor level to facilitate cleaning benead them. If the radiators are fixed elsewhere than under a window, a shelf can be fittec about 75mm above to protect the wall frorr staining.

Painting radiators is no problem, bul metallic paints such as aluminium car reduce overall output by up to 10%.

Skirting heating and fan convectors

The same principles apply except that it ix not necessary to have valves at every poinl on the skirting heating beyond a balancir4 valve for the circuit.

Pipework and fittings

When installing copper or steel pipework ii is vital that the pipework is cut squarely and then cleaned thoroughly with wire wool inside and out at the ends. The same cleaning is necessary for fittings otherwise the joint, especially soldered joints, will nol be leak-free.

Use as few fittings as possible and try tc install long lengths of pipework. This will reduce the phance of leaks and friction losses. All bends should, where practical be formed using the bending springs. Never kink pipework when bending as this reduces the flow of water and causes noise.

Always lay out pipework either level or at a gradient to the point of venting. Do nol be afraid to put in as many automatic air vents as you feel are necessary. About 90% of the faults on heating systems are due to air locks. Make sure that each compression fitting is tightened, but not over-tightened which will strip the thread or burr the olive ring inside.

If you are using capillary connections try to make them before placing them under the floors, to reduce the fire risk and possibility of leaking.

Pipes should be clipped to walls and joists at short intervals: Points to note when installing

When lifting floorboards try not to splinter them.

Never put banks of pipework in the centre of a room as this is the weakest point of the joist. Try to run pipework with or under joists. Make notches cleanly and if making holes through joists make them through the centre.

Never fit pipework side by side. Make enough room in the joist for a gap to allow for expansion. Many installers place pieces of felt between pipes.

Modern thinking is that all pipework under floors should be insulated to save heat.


Decide where the valves are to be fitted. Usually they are at the bottom, at opposite ends, which leaves the two top ends: one of these is blanked off with a plug and the other is fitted with a brass air vent valve. These are threaded and must be wrapped with PTFE tape and screwed in with a spanner. When fitting the air vent make sure that a key can be fitted in the end when the radiator is installed, so that it can be vented to release trapped air.

Steel panel radiators are hung on brackets (supplied) and fixed securely to the wall. You must take care to align the brackets horizontally because radiators that are not

CPVC pipe

An alternative to copper pipe is the CPVC (Chlorinated Polyvinyl Chloride) hot water pipe system which is now available on the UK market. This plastic material has many advantages, for instance it is corrosion resistant, lightweight, reduces heat loss from hot water, and is impact resistant. CPVC is available in 15mm and 22mm sizes. Joints are solvent-welded.

Working systematically

You must work systematically, firstly because putting in central heating is a reasonably dirty job, and secondly because in most households it is a problem to find enough storage space, unless a garage is available.

It is practical to make as many joints and connections as possible before the actual installation.

This is one system of working when installing a new system:

1. Put on overalls. Assemble all fittings, tools and materials.

2. Flush out the radiators, preferably with a hose to remove any sediment.

3. Fit lockshield, wheel valves, plugs and air vents.

4. Prepare and fit boiler connections to receive pipework, and pump if fitted inside.

5. Prepare and fit expansion tank connections.

6. Prepare and fit cylinder connections. Take great care when screwing up the joints to a copper cylinder because the cylinder walls are easily distorted. Fit immersion heater to the cylinder. This will allow you to have hot water until the boiler is working.

7. Install radiators or convectors.

8. Prepare wall or base and install boiler.

9. Install cylinder in position on two 100mm x 50mm wooden battens to allow air to circulate below the cylinder. This also allows a drain cock to be fitted at the lowest point.

10. Now you can lift all necessary floorboards since all the equipment is in place ready to receive the pipework.

So far the household has not lost its gas, or hot or cold water supplies, due to basic planning, and you have not had to enter the loft area. The next steps will help reduce the time that these services will be disturbed.

11. Connect up all the equipment with pipework as necessary.

The gas board must:

12. Fit the gas supply to the boiler. This can usually be taken from a branch fitting, made on the outlet side of the meter. Be sure that the pipework size is that required. It is usually shown on the inside of the boiler casing. Check with your gas authority


The pump can be fitted in the flow or return, next to or in the boiler or next to the hot water cylinder. However, it must be installed in an accessible position and in the correct plane according to the manufacturer’s recommendations.

Boiler and flue or chimney

Boilers should always be placed on a level base which is made of non-combustible material. When installing a wall-hung boiler be sure that you use the template provided.. Never install a boiler adjacent to or touching any kitchen units or furniture unless it is specifically designed to be installed in this way. Leave a gap of 75mm around the boiler. Remember that it is a machine and has to be serviced.

That the supply pressure is adequate to meet heating need, and, most important, never light a match until the supply is shut off at the meter.

Secondly, meet all the requirements for air supply to the boiler. These can also be obtained from your gas board.

13. Position the F & E tank in the loft, level with the cold water tank. You may need to make wood supports. Connect up all the pipework, but leave the cold water main connection to last.

14. Shut off the cold water main at the stop-cock internally or externally. Make the final connection to the F & E tank and from the cold water domestic supply make the connection to the cylinder.

15. Fill the system, check for leaks. If there are none flush out the system two or three times, pour corrosion-inhibitor into F & E tank and finally fill system.

16. Vent the system through the radiators when the valves are fully open and leave them open.

17. Wire in all thermostats and electrics.

18. Switch on the heating and balance the system through the lockshield valves. Balancing means to regulate the flow of water through each radiator so that the temperature drop (inlet to outlet) is equal on all radiators and gives the correct temperature in the rooms.

19. Check that all the controls are working satisfactorily and the heating and hot water is reaching temperature.

20. Make a final check for leaks and loss of pressure, particularly with a sealed system which operates at higher temperatures and pressures. As air is expelled from the system water levels have to be topped up. This is done automatically from the F & E tank.

Keep your system moving

Once the heating system has been installed, and all the checks made for leaks and air locks, it can be left for a couple of months. Then once again check for leaks and airlocks. If there are any, which is quite possible, they must be put right straight away.

If a radiator does not become hot at the top after venting then the level of the radiator is out. Close down the valves. The lockshield valve is closed by unscrewing the cap and then with a spanner turning the spindle clockwise.

The radiator can now be taken off the brackets when the compression joints have been loosened and the water drained off into a bucket. The radiator is then re-aligned, reconnected, filled up and vented. This usually cures any problem.

It is usual to clean the boiler once a year. This job has to be done exactly as the manufacturer recommends and it is best tackled during the summer months. It is not necessary to drain the system.