Step-by-Step Radiator Rebuilding Tips

Check and recheck required components of a radiator rebuild before starting work

The most important points to remember, during a household radiator rebuild or replacement, relate to researching the type of radiator you have, accurately measuring the sizes of all the individual components you need and thinking carefully about when to switch off your heating system so you can drain the old radiator without causing cold damage to the property.

Preparation

Identify which type of radiator you have. Measure the dimensions of the radiator you need with a measuring tape for a complete radiator replacement. Record the height, width and depth of the radiator. Purchase the replacement radiator or radiator components from your local hardware store. You will need a thermostatic radiator valve with a temperature selector, a spindle valve, fresh solder and 8, 10 or 15 mm valve-to-pipe connectors called "straight couplers." If you are connecting two different-sized components together, such as a 10 mm thermostatic valve and an 8 mm radiator pipe, you will also need an 8 to 10 mm converter. The standard size is 15 mm, according to Drayton Controls. When you are sure you have all the correct components, including any converters, you will need to switch off the entire heating system -- not just the radiator you are working on. Prepare for the house becoming cold. If you are working during the winter months, create back-up heating with electric heaters, a wood-burning stove or oil heaters.

Repair

Pull back any carpets and underlay to avoid water damage. Drain the old radiator by unscrewing the nuts and bolts at each of the two end valves with a wrench. Catch any leaking water in a bucket or use a wet/dry vacuum cleaner. Lift the radiator off the wall brackets and set it aside. Clean the radiator if you need to use it again; otherwise, discard it. Solder any broken pipework or split joints in the adjoining pipework with a soldering iron and fresh solder. If a valve leaks where it joins to the pipework, repair it. This is a compression joint so you will need a replacement olive (like a bolt but thinner and smoother) to create a better seal for when the nut is tightened. You can also wrap new joints and old joints with a small 1- or 2-inch length of polytetrafluoroethylene (PTFE) tape. Any more and the bolts or olives won't fit back on.

Refit

Insert the 8 to 10 mm (or 10 to 15 mm) converter into the 1/2-inch tailpiece -- the common sizing for the thermostatic valve (the threaded nut that connects the thermostat to the radiator). Fit the thermostatic valve onto the radiator so that the thermostat controls the temperature of water inside the radiator (the input end, to catch the water as it flows into the radiator from the boiler output). Screw the thermostatic control onto the top of the thermostatic valve and tighten it with the wrench. Bolt any straight couplers onto the pipework to convert 8 or 10 mm pipes to 10 or 15 mm and tighten them with the wrench. Clean or replace the wall brackets. Paint the wall behind the radiator if you wish. Rehang the radiator loosely. Secure the two end valves with the bolts and wrench, adding PTFE tape if required, until the radiator begins to fit neatly and securely to the connectors and pipes, then tighten everything fully.

Planning

For extra protection against corrosion and to prevent damage caused by "pinholes" (corrosion spots due to sludge or excessive air in the system), inject a corrosion inhibitor into the highest radiator in your property, such as the one in the bedroom or converted attic space, whichever is physically higher up than all the others. Do this while the system is switched off and the radiator has been drained, then refill it with water and switch on the system once it is fully secure and air-tight. Test the radiator at low temperatures.

References

• Drayton Controls: TRV4 Thermostatic Radiator Valve
• Bumford Heating Limited: Radiator thermostats for domestic 2-pipe systems RAS-C2 range (PDF)

Resources

• Danfoss: Thermostatic Radiator Valves -- See How They Work
• DIYDoctor: Sizing Radiators