Three questions:
permanent, presumably neodymium
The magnet is within a tube, the crud collects on the outside of the tube, for cleaning the tube+magnet assembly is removed from the filter, then the magnet is withdrawn from the tube, the cruc can be washed-off the tube
Various videos just show it going down a sink, it's mostly just rust, isn't it?
Some have the magnetic collar on the outside of the housing and, as you indicate, the magnet is first removed. For the (boiler manufacture recommended) filter fitted to my system the magnet is first removed, a tap on the bottom of the filter is opened and the water pressure forces the crud out.
Other filters have isolating valves either side of the filter allowing the filter to be opened for cleaning. These also have the advantage of being a good place to for dosing the system with CH additives (inhibitor etc.).
One of the latter two.
On mine (Fernox TF1) you:
Make sure the boiler will not fire during the cleaning process Close the butterfly valves either side of the filter Unscrew the bleed valve at the top (to allow air in) Withdraw the magnet Open the drain valve at the bottom of the filter.
Once it has emptied:
Close the drain valve Replace the magnet Open one butterfly valve, and allow air to purge from the vent When purged, close the vent Open the other butterfly valve
Drain will be fine.
Neodymium.
In my version, the magnet is in a tube, sealed from the water. Turn the water flow off (boiler off), pull the magnet out of the top, the collected oxide drops down, then you open a drain valve at the base, where it all collects, to flush it clear.
I don't see why not, it's only magnetite.
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