I have a Potterton Promax HE boiler which has recently started to leak with water dropping from the yellow plastic nut/cap at the bottom (appears to me to be an overflow for condensation). Any suggestions on what I could do? One thing I did find when I undid the nut is that there was a lot of grainy grey matter around the nut on inside of the plate.
Many thanks in advance.
Many thanks in advance.