Well I went back and looked for the spec you said you'd posted and couldn't see it. Look, you're WF client. The installers are WF representitives or agents. They quoted a price to bring the job to the WF spec. I shredded mine when I finished but a powerflush was on it. Even if it wasn't the boilers had to be installed in accordance with manufacturers instructions. If the installers didn't do it then they did not do the work they'd contracted and priced for. Carillion want you to go away. Don't bug us bug Carillion. If you get no response go higher or to an MP. Ask for a copy of the Spec for gas installations (I can't remember the title) if they fob you off FOIA will get it for you there's nothing commercially sensitive about it. Pay a local engineer with a test kit to take a sample or do it yourself and use a TDS meter it or send it to Fernox they'll test it for you and also tell you whether one of their cleansers and inhibitors were used. Personally I'd do that after asking for written assurance from the contractor that this had been done and without telling them of your intentions 'cos you have them by the nuts if they say yes and it's no. Fernox charge less than a £100 and you say you don't care about the money. What have Remeha got to do with anything? Did I miss something? or Vaillant? Ideal is the boiler manufacturer. Your problem is the scheme is ending and that's that. On the plus side there'll be something to replace it and Carillion will be looking to get a slice and unfinished business doesn't look good. Stop writing here and get at the people who you need to but post back with results otherwise you're just an all talk Moaning Minnie (with a masters in chemistry).