The guy tried to remove the tube connecting the pressure meter, it was in such awkward position that he was unable to take it out and put it back in. If he could not put it back in, then the boiler would have to be replaced. He was on a time charge, anything more than two hours would have cost...
I had the engineer in. Looks like it is just the one valve you need to turn on this model.
Unfortunately the system had so much sludge, it even blocked the pressure gauge. The little cable that connects to the gauge was in an difficult to reach position (back of the boiler), the engineer...
@Agile, I let it for about 2 minutes. Initially it made a loud water flow sound which eventually stopped.
I have hot water, but no central heating. I was told by valiant that we should stop using it like this, as it will cause damage. They want 200£ for an engineer to fill it!
This is a follow up on the thread how to refill Vaillant Turbomax 824E //www.diynot.com/forums/plumbing/how-to-refill-vaillant-turbomax-824e.317627/
There is only one screw valve and not two like all the other guides I have read.