Leaking bleed device

[pete39]

Advice please

Next to my hot water cylinder is this pipe sticking up with some sort of bleed device on top and from here it is leaking.
I have tightened the red plastic knob as much as dare.

What do I have to do to cure this leak, something simple I hope?

I have downloaded a couple pictures of the upright bleed pipe and the plastic box that connects to this pipe,

Thanks Pete

[plumbbob]

As you know this is the automatic bleed valve which contains a float valve that opens and shuts to allow air to escape.

Good news!

Do you see the where the white ptfe tape is showing just above the compression connection to the pipe? The top part can be separated here by unscrewing at this point.

[pete39]

Thanks plumbob, I'll give it a go.