Vaillant 828e strange problem.

[Bouba]

My combi boiler works fine. I had an issue with the water pressure rising,and this was tested by the gas engineer. He charged the expansion vessel and water pressure was fine for few days.

Now a strange problem has come up. Heating and hot water is fine, but next to the pump there is a small black cap(i believe its called de-aerator) on a round small closed unit. Its leaking water from the top, not a lot but enough. Also the water pressure is rising again.


The engineer used a descaler for the heat exchanger. Could he have messed up something. Please point me to the right direction.

 

[ianmcd]

the component you refer to is called an automatic air vent or AAV and it is common for these to leak, it may have a plastic cap on it, like a dust cap on a tyre, if it does just tighten this down as a temp measure and it will stop leaking until you can replace it, as for your boiler pressure rising does it rise when the heating is switched off or only when the heating is switched on ?

 

[Bouba]

Thanks. So the leak is from the black cap. Does this come as a whole unit or I can just buy the cap. I can see the drum is attached to the pump.

The pressure rises when heating is switched off.

 

[Agile]

Its the inside which leaks.

The existing cap can probably be tightened to stop the leak.

Its usually the same size cap as a car tyre!

Tony

 

[Bouba]

The top section of the drum where the black cap sits can be opened with a wrench. It has a mechanism in it,silat to a cisten units like a ball cock.

Can this be cleaned. What part do i need to buy. Would this be whole pump as this part looks like 1 complete unit.

 

[ukgas]

Pressure rise is likely caused by a bypassing fill block. Common problem. Still happens on the newer models. New fill block required, easy to change and not an expensive job. The air release is a screw on jobbie, cost me about £10 last time I bought one, again a common problem.

 

[Bouba]

Thanks a lot for the input everyone.Finally what is the part number of the air release screw i need please.Does it come as a whole unit or single part.

 

[ukgas]

061707 for the air vent. 014675 for the fill block.