Advice with this leak please

[Jupiter01]

One of these joints is leaking. Not quite figured out which one. It caused the combo boiler pressure to drop.

Do they need undoing and then tightening up or is it safe to tighten them up whilst we are at full pressure? Feels a bit odd writing that but please excuse my ignorance.

 

[Wayners]

The valve insert will need removing and PTFE tape used

 

[Jupiter01]

The valve insert will need removing and PTFE tape used

Is the nut on the rad one of those that has a rubber seal or something and doesn’t need to be too tight?

With the other one that is using the plastic pipe, is it the insert you are referring to?

 

[terryplumb]

You need to establish exactly where the leak stems from.
Is it the union that connects the valve to the rad,or the valve to the supply pipe,or is it from the valve body ?