Vaillant EcoTec Plus 831 Not Fill with filling loop

[Martin Byford-Rew]

This is an odd one. Our Vaillant EcoTec Plus 831 will not fill when using the filling loop. It used to fill fine using it but now it does not. What is odd is that there is no sound of filling at all. It makes no effort. Water is flowing through the filling loop as I’ve disconnected it and checked so that is not the cause. Has anyone seen this behaviour before and what is the likely reason?

 

[picasso]

The plastic of the tap gets rounded off so it feels like the valve is opening but it aint, use a small screwdriver to remove the plastic tap and use a spanner .

 

[Martin Byford-Rew]

Thanks, tried that but still the same. No water flowing into the boiler through the filling loop.

 

[ianmcd]

post pics of the filling loop, both ends

 

[Martin Byford-Rew]

Not sure how having pictures will assist but please see below. Thank you for your assistance. Just to be clear, water will flow through the filling loop when tested by disconnecting from the boiler in end and turning on at the water mains flow end.