I had a Viessmann boiler installed 3 years ago. It worked like a dream and we were delighted with the money we saved on our bills until 3 weeks ago, when water started to pour out of the boiler. When the Viessmann engineer came out to it, he identified the faulty hose that had split but refused to fix it under warranty because of the dirty water in the system, saying I needed to get a magnafilter fitted and that my 5 year warranty was now invalid. The boiler had been annually serviced, as per their advice, and nowhere in their literature does it mention the need for a filter. I subsequently found that repairs, when there is dirt in the system, are carried out at the engineer's discretion. I was told twice, by one of Viesmmann's own reps, that if a different engineer had called it would have been repaired and I would have been advised to get the system clean and have a filter installed. After being without hot water or heating for 3 weeks, I had to pay my original installer to come and sort out the problem, which I never thought I would have to do on a boiler installed and serviced by approved and qualified engineers as per the manufacturers instructions. Their so-called customer service agents were disinterested and patronizing, and spoke to me as if I had done something wrong. The product is let down by the shocking after-sales service, which in my case was non-existent. Installing a Viessmann proved to be an expensive and stressful mistake, costing me hundreds of pounds in repairs and hours of telephone calls. My advice would be to avoid them at all costs.