Hi I have a ferroli Modena 80e boiler & underneath the pipe on the left (radiator pipe I think) is leaking where the tiny screw goes but the screw has lost it's thread so I can't tighten or loosen it? & this is making the pressure drop.

I am not familiar with the type of Boiler you own - but generally speaking - if the screw has no thread, replace it with new screw. If the female thread is stripped too, than you will have to re-cut the female tread so it accepts the screw.

Hope that helps / Milo

If you go to the ferroli Modena 80e boiler manual, in pag 6 you can see the number parts. Can you specify where is leaking in the draw? Your pressure in the gauge says what?