This article discusses refinishing reclaimed cast iron radiators and adapting old radiators to accept modern valves. It doesn't discuss resizing reclaimed cast iron radiators.
You'll first need to remove the old paint. The best way to do this is sand blasting. There are many companies that provide a sand blasting service, including Blast Spray & Polish in South East London and Rustproofing in Stockport. Once stripped back to the bare cast iron, it’s best to prime the radiator to prevent rust – freshly exposed cast iron rusts very quickly.
This is the point at which to think about connecting the radiator to a modern central heating system. It is unlikely that all bushes and plugs (see the image below) will fit a modern central heating system so you may need to replace some. All cast iron radiators will have two reducing bushes, also known as valve bushes. These are the point of entry and exit for the water and are usually located at the bottom of the radiator. It is the reducing bushes that are most likely to need replacing to fit a modern central heating system.
At the top of the radiator there will be one blanking plug and one bleed bush. These are less likely to need replacing unless they are broken or in the wrong position. To remove, unscrew the bush or plug using a spanner. All reclaimed cast iron radiators that we have come across have right-hand thread bushes and plugs, so unscrew to the left. The insides of reclaimed cast iron radiators are usually pretty rusty so they require a good amount of torque to unscrew the bushes. We tend to use a short piece of scaffold pole to extend the length of the spanner handle and provide more torque on the bush.
Most modern thermostatic or manual radiator valves have a 1/2″ BSPT (British Standard Pipe Tapered) connection to the radiator, which equates to a 21mm hole into which the valve tail is inserted. Castrads can supply a large range of bushes that will reduce the hole in the radiator down to the 1/2″ BSP size required to connect a valve.
A little aside about BSP sizes: British Standard Pipe fittings come in parallel or tapered thread. The fittings on reclaimed cast iron radiators are usually BSPT (ie tapered). The seal is made at the contact between the male and female threads with their tapered shape meaning that the contact area between the threads increases with each turn. To ensure a strong seal is acheived, it is absolutely essential that a good sealant is used when screwing in the end bushes. This is because cast iron, especially reclaimed cast iron, is often pitted. For this purpose, we recommend LSX Sealant.
Once all four ends are sealed and you’ve checked that the bleed valve is working (if not you can buy new bleed valves from Castrads), you’re ready to connect the reclaimed radiator as any other new radiator, though you’ll probably want to paint it first. Castrads’ spray paints are all available in aerosol cans or larger 5L cans.
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