Thank you all for your posts. I considered the weeping hole as well but dismissed it as I was concerned about the presence of flammable vapours.
I would like to review the use of these ‘poly covers’. Does anyone the technical name for these??
Many thanks again.
I have a small problem in my plant with vent lines. The current design has the tip of the pipe slightly angled (45 deg) to prevent rain water entering the main system. But this is not sufficient and it is important for the system to remain dry. I am tempted to increase the angle to a full 90deg...