We get regular calls from householders complaining that they aren't getting sufficiently hot water from their combi boiler. This can be caused by several single factors or a combination of them all. It maybe an undersized gas supply to the boiler. It could be a budget / DIY store boiler {I won't name them} which are cheap to buy but have very poor hot water flow rates to start with. The boiler itself could be undersized for the hot water demands placed upon it. Many boilers were 'found out' over the past two severe winters as the incoming cold water supplies from our resevoirs were colder than they have ever been in recent times. In many cases it was coming in to properties at just 2 - 3 degrees C. Even after the combination boiler had raised the water the standard 35 degrees C it just wasn't hot enough for showering or bathing in winter time. One of the most common causes of poor hot water performance in combination boilers is a scaled or sludged up water x water plate heat exchanger. The picture shows a cross section of one which I cut open out of interest after we had replaced it. The heating waterways were full of sludge and the domestic hot water ways were showing signs of limescale formation. After flushing this system out and replacing the water x water heat exchanger we have treated it with corrosion proofing inhibitor to protect the heating side. A limescale filter has been installed on the incoming mains cold water service to help combat limescale formation on the hot water side. Sometimes in less severe cases chemical treatment can cure the problem without the expense of swapping the heat exchanger. In this case it failed. The best cure of all is prevention by treating new systems correctly, installing limescale filters as standard and ensuring old system which new boilers are fitted to are properly flushed out & cleansed. Lastly and perhaps most importantly; don't buy cheap DIY store boilers. Whilst you may save a few pounds on the initial purchase, the life time cost {over priced parts and unreliability}of these poor quality appliances far exceeds that of the good quality brands. We are always happy to advise on on any hot water issues you maybe experiencing.
