Sentinel System Filter - which is the inlet

[jonc123]

I have a "new old stock" Sentinel System Filter. It is the brass one, but not the one with a removeable magnet. https://www.gassupportservices.co.uk/f/m/Sentinal/Data Sheets/System Filter.pdf
The fitting instructions do not state which is the inlet port. I'm guessing that it the lower one. I'm thinking that if it is installed the wrong way around, the accumulated debris will get trapped on the wrong side of the filter and be impossible to remove without disassembly.
Can someone confirm which port is the inlet?

 

[cross thread]

As they are normally filled on the return pipe it will be in at the bottom

 

[jonc123]

Thanks - that is what I was thinking. Given that some boilers are top feed (mine is), you would have thought that Sentinel would have provide the details though.