I have a Vaillant Turbomax boiler (unsure of exact version as I don't have the manual).
The pressure is a little low so I'd like to refill. I've followed these instructions:
("Turbomax Filling Loop Mechanism" section)
But nothing seems to happen when I turn both screws 90 deg. I can't hear any water flowing and the pressure isn't changing. Any thoughts? I'm currently on about 0.5 bar. Many thanks