I bought a replacement water filter. Pozzani GS10J. The instructions are ambiguous. Has anyone replaced this cartridge and can shed light? In the first photo you can see the plastic supply pipe is attached by a jubilee clip to a black plastic fitting that I believe would have been supplied by Pozzani as it seems to screw into the cartridge. The second photo shows the replacement, which has a silver foil cap stuck to the inlet and also a red locking clip. If I unscrew the black plastic fitting from the old cartridge how do I fit it to the new cartridge? Remove foil cap and the locking clip? Then attempt to insert the black fitting? The instructions talk about push fit. So push fit the black fitting then tighten with spanner? I'm sure it's all dead simple when you've done it once.....