potterton suprima 50

[tonell31]

hi, have 2 rads that are cold with one of these boilers, i want to take the rads off and fit new valves to them but cant find the filling loop.
there is a drain off on the 22 pipe coming out of the top of the boiler but no filling loop
help

 

[stevetheplumber]

probably open vented system tie up the ballvalve in the small tank in the loft