I have 2 problems but the 1st is this: I have drained a few litres or so of water from my heating system after putting cleaner in it via the feed tank which is high in a cupboard upsatirs in our bedroom. (says to leave it in for 4 weeks) but now there seems to be an airlock - i presume this as the boiler won't start now. the pilot went out and won't restart. is this because i drained water out and air got in through the feed tank? or is it a coincidence that the boiler won't start? wjat can i do please