Pressure gauge showing zero on red expansion vessel

[Macca4]

New to this so please bear with me! The pressure gauge at the bottom of my red expansion tank is showing zero. However my radiators are getting hot and boiler seems to be operating okay. I did bleed a bathroom towel rail yesterday which only had heat at the very bottom. Not a massive amount of air came out but seems hot almost to the top today. I added a bit of water using the ‘loop’ feed at the bottom of the tank today and could hear the water going in. But the gauge has stayed at zero. Faulty gauge maybe? Unventilated Ariston system with white and red expansion vessels.

 

[ShaunCorbs]

Try running the water for a bit longer via the filling loop

 

[Philip Duff]

I have to put water into the expansion tank every couple of days. Surely this isn’t correct