On Monday, 26 March 2018 20:12:30 UTC+1, Tim Lamb wrote:
As heading. I now have 2 vents out of 6 which dribble water when
unscrewed.

Any thoughts?

How do they work anyway?
--
Tim Lamb

They have a little float in them. If air appears, it falls ans opens a valve in the top.

You can dismantle and clean any crud out and clean the valve seat and needle. (They can stick a bit or get something on the valve seat.)