Just had Vailent out to see to the boiler it not the boiler it's the filter, it was fitted at the same time as the boiler, but he said it isn't anything to do with them, paid almost 4 hundred pounds a few weeks ago,But now have to get a plumber who can change the filter, I put a bowl under the filter the bowl after hours is dry,chck again later,when the heating has been on for a few hours,