There was a time when every centrally heated home was fitted with a large, cumbersome cast iron radiator that not only took up a large amount of space but also were not especially efficient by modern day standards in heating. These traditional radiators ran on a single pipe system where water was heated to create steam that was then pumped up through the pipe in the radiator. As the steam cooled, the condensation would run back down the same pipe to be re-heated. In the past few decades, double pipe water heating has largely replaced the old system. Here, the water itself is heated and pumped into the pipes to heat the radiator. As it cools it runs down a separate pipe on the opposite side and back into the boiler to be reheated.
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