Central Heating Filter Installation
This photo is from a cupboard in my own home. Most central heating installers will now fit a magnetic filter as part of any new installation, to remove magnetite or "black sludge" from the system. My boiler was installed before these filters became readily available, so I drained and flushed the system and retro-fitted this one myself.
These filters help to keep a CH system running efficiently (cold spots towards the bottom of a radiator are a sure sign of sludge build-up, whereas cold spots at the top of a rad usually indicate that the radiator needs bleeding), and prolong the life of your boiler by preventing the plate heat exchanger becoming blocked with magnetite.