Vaillant aqua plus water pressure low

[David Thorn]

Hi, my ten plus year old Vaillant aqua plus boiler water pressure is low, however its not a conventional valve top open, I've purchased a
key filling valve - below, unfortunately it doesn't fit the valve due to valve being previously opened with a flat screwdriver which has misshaped/worn out the valve. I've read somewhere that I could leave one end of the loop open to slowly increase pressure, is this correct? I've uploaded a photo if anyone can help!

VAILLANT AQUA PLUS VUI 362-7 & 362-7 R3 FILLING VALVE HANDLE KEY 125151 ORIGINAL | eBay

 

[chris watkins]

No David not a good idea,
1. The Water Regulations state the flexible loop should be removed in-between use, of course nobody does but leaving one side open all the time increases the chances of the other valve letting-by & overfilling your system or allowing back flow of dirty heating water back into contaminate the drinking mains.
2. The flexible filling hose may burst under the mains pressure if one side is left open.
The answer is to leave the one in the boiler with both valves closed and add a Part L complaint filling loop to the system, if you have room below the boiler.

 

[David Thorn]

Thanks, got a local plumber in to look at the problem. Unfortunately looks like a wider issue with the boiler where a load of gunk from the very old radiators has got into the system. Though the plumber first added a filling loop and drained the system, whats odd is the loop is connected below the filter which I'm not sure would have led to the boiler being full of gunk in the first place. I'm not a plumber so obviously dont know these things. Your help is much appreciated.