new vaillant 831 -pressure gauge in red

Hi, I have a similar problem with my boiler, pressure is always in red even when filling loop closed. I managed to take waterout via pressure relief to 1.5bar. Within 30min the pressure had gone back up within the red area. I was just wondering what was the outcome of the problem listed by nigelad. Thank you. Any advice will be welcome. P.S at what pressure does PRV open? And why doesnt it open if my boiler is alaways in red.
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As usual the OP did not post the outcome.

However, I expect it was the old filling loop leaking.

Apologies Agile!
You were right though.
It was the islolating valve on the filling loop that meant it was leaking into the system.
Might have been a factor in the old boiler problems?
Anyway, the installer came back and sorted it.
New boiler has just had 1 year service and we are very pleased with it. Apparently the magna clean was almost spotless!
BTW my installer left the filling loop connected to my Ecotec 824 plus, and both of the grey filling loop valves were letting-by. Grr.
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Ur supposed to leave the hose connected on the inbuilt fill loop, it's only external ones that need disconnecting
With the number of grey knobs rotating on the shaft its very convenient if an old filling loop is available for easy toping up.

I am not a fan of built in filling loops.

Cannot think of one model with well designed ones!

Apart from the Linea! But although they were well made and designed they also too easily became blocked up!

Ur supposed to leave the hose connected on the inbuilt fill loop, it's only external ones that need disconnecting

The Vaillant manual says that the filling loop does have a double check valve, but is also insistent on removing the loop "Close both stop valves after filling and detach the filling device by pulling the double check valve from the cold water stop valve."

and elsewhere "The system can be filled using the built in filling loop or via a separate filling point fitted at a convenient position on the heating circuit. The connection must be removed when filling is completed."

Having checked up on the regs, domestic CH circuit water is defined as category 3 (hazardous to health if used for cooking or drinking etc.) - so as long as there is at least a double check valve in series with the filling loop, then the loop can be left permanently connected in the UK for a domestic boiler (and also for a commercial one in a system less than 45 kW) I think.

and Public.pdf

... so I suppose Vaillant just don't want users accidentally opening them (and leaving them open) - or perhaps they just want to write one version of the manual for multiple jurisdictions.
I have a Vaillant ecoTEC plus 831, installed in 2010. I have a problem with both valves at either end of my internal filling loop letting by on this boiler. I think that capping off both valves will be the most simple solution. I think that the mains supply side requires a 1/2" cap. But I am not sure about the CH side. Does anyone happen to know which type of caps I can buy to cap it off? Or if there is another simple solution, I would be grateful for any advice.

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