Magnaclean - flow or return?

[Calmore]

Planning on installing a magnaclean/spirovent/other type of filter on my combi boiler in a few weeks (Once I have fixed it!).

From a practical perspective does it matter if this is installed on the flow or return pipes? One pipe is easy to get to and the other a PITA...

 

[jackthom]

Modern boilers with more restricted heat exchangers don't take kindly to particles (especially lumps) of magnetite flowing through them and can end up becoming partially blocked.

So the most logical location for this sort of filter is on the return just before the boiler.