I have an Intergas Combi installed 15 months ago to the loft of our bungalow and have been installing new drainage for a bathroom and en-suite with an internal stack. I took the opportunity to connect the condense drain (32mm) to the new internal stack to reduce the dreaded freezing risk and noticed that the trap on the condense has an amount of black gritty deposits in it. I realise that this is probably aluminium oxide? If so is my boiler being eaten alive? Gulp! (Water is softened but Intergas confirmed this is fine with their boilers).