Trouble pressurizing Vaillant 824

[YeezPeaz]

Hi all

Thanks in advance for any help! I bought a property recently with a 12yr old Vaillant 824 combi boiler. It seemed to work fine initially but after a few months the pressure dropped to almost zero.

I looked through other threads in this forum about pressurizing the system, and followed previous instructions by turning the two valves on the bottom to refill the system. However rather than hearing a "hiss" and seeing pressure go up, this does not seem to work at all. Note: the same drop in pressure happened a month ago as well so I called out a plumber who tried the same with the valves (also did not work) so he had to "reverse fill" by pumping water from a shower hose back into the CH system via a towel rack in the bathroom - kind of complicated...

Ultimately, does anyone know what would cause turning on the two valves to not fill the system? Scaling from hard water? Any ideas how to fix this problem without another expensive call-out from a plumber?

Kind regards
Yi-Hua

 

[flameport]

One or both of the valves has failed. Replacement is the only option.

Would have been better if the 'plumber' who visited last time fitted new ones rather than do what was obviously a temporary bodge to get water into the system.
There is also the question of why the pressure dropped in the first place.

 

[dang32]

I would say one of the plastic knobs has rounded off. to temporarily repressurise remove the plastic knobs and open with a spanner but of course the longterm solution is to get an engineer to replace the valves and find the reason for the pressure loss

 

[dilalio]

Make sure you call someone who works on Vaillants. That way they will know exactly how long it will take them to replace the filling loop part(s) and where to get them. Alternatively, if the installation has scope, you could bypass the built-in filling loop and install your own one, elsewhere on the pipework... Anywhere you have cold mains near to the CH circuit.

 

[AGAS]

are you sure only one of the plastic knobs rounded off but both. I've had them feel tight but still not turn the valve . try taking both plastic knobs of and adjusting valves ,if you haven't already checked, just a thought . still got to sort the pressure lose thou