Plumbing in an american style fridge freezer?

Hi
Just purchased one of the above. Also bought a Y connector to feed off the cold tap of the washing machine and a brass adaptor (one end fits on the Y connector, the other connects the feed on the fridge) My problem is, no matter how tight i make it, and even though I'm using an olive I'm still getting water leaking from where the fridge freezer pipe connects into the brass adaptor - No idea what to do next - Can anybody help?