Installing magnaclean on gledhill boilermate

[PhoenixServices]

Got to install a magnaclean on a boilermate and flush the system.

Would you guys install it on the return to the boiler. Or the return from the rads?
Not sure which will pick up the most muck.

 

[Alex Knight]

Return from the rads I would have thought as the boiler to boiler mate is just a loop?