how to refill combi boiler/system with digital display

[dilly38]

Hi I'm new here...
I have a 10 month old Vaillant ecoTEC plus 825 combi boiler which so far is excellent. I am refurbing my bathroom and putting in a new towel radiator and new valves and some pipework and so need to drain and refill the system. I have read both FAQs on this, but as the pressure is displayed digitally how can I check the pressure without switching the boiler back on? Is there an analogue scale (like a small Bourdon gague) inside, or do I just fill it until water comes out of a bleed screw, switch back on and check the digital display?
When draining down do I need to do anything to the boiler, apart from turning it off, as I've seen Youtube videos where the guy talks about 2 and 3 way valves in the boiler.
My draincock is on a radiator which is higher than the pipework I need to change so will I get all the water in the lower pipework come out when I cut into it, or will it syphon outside in the hosepipe?
Finally, is this boiler up to running a thermostatic mixer shower? I have a 2 bed flat with one bathroom and was told by the guy that flushed my new boiler that I had good mains pressure.
Any advice really appreciated, thanks for reading.

 

[Agile]

So you want to lose all the inhibitor the installer should have added?

I suspect you are heading for problems. Make sure the installer is available should you need to call him.

Tony

 

[dilly38]

Thanks for the reply, but I just need to know about the digital pressure gauge and whether I need to do anything more than open the drain (which is only there because I fitted it 15 years ago when I last had a new boiler 15 years ago as I hung the radiators before the CORGI plumber did the boiler) and some bleed valves. I fitted the current bathroom 17 years ago and there has never been a drop of water due to a leak. The only time I have had a leak was when my new boiler was flushed after fitting, when the flush man (?) did not refit the washing machine supply which he used for the flush properly. It leaked and ruined the brand new double unit under the brand new sink and worktop, all of which I also fitted. Seriously what problems do you think I might have? The inhibitor is Center central heating inhibitor which is about 9 pounds at plumbcenter. I think you can see why I'd rather do this myself. I did have a plumber due to do the pipework a month ago. He never turned up.

 

[Agile]

Do you think that the own brand at £9 is going to be as good as the market leaders Fernox and Sentinel which are close to twice the cost?

Sounds as if you are trying to do it on the cheap and to a lower standard.

Tony

 

[DP]

Dilly, shelf the idea of replacing a proper radiator for a shiny chromed towel rail. You might be hard pushed to get one that matches heat output of present radiator

WRT radiator and valve replacement. You do not need to empty the system, only drop the pressure to zero. As long as you do not have two open ends, you will most likely retain bulk of water ( and treatment ) in the system. Once alteration done vent new radiator and pressurise the system. Mind you, boiler will need purging too, where you may have difficulty

 

[Agile]

Following on what DP has said above, it is possible to do more in that respect.
That is to turn off both valves on each end and the flow and return at the boiler.
That will retain virtually all the water in the system and all you will need to do is depressurise the pipework which will usually only involve losing less than a litre if upstairs.
Tony