i have a ariston eco 35mffi c ombi boiler.The central heating works fine,but the hot water(dhw)starts fine, then ends up as a trickle.If i play with the tap i can get a bath full of normal hot water but at a much reduced flow.Everything else about the boiler functions normal. I am not a plumber but am an engineer. I may be totally wrong ,but i suspect the secondary heat exchanger may be scaling on the dhw feed. Any help would be most appreciated,thanks. I fully understand my limits,and would seek professional if u think i am on the right track.

tony, October 2013

Hi Kash, for the benefit of future inquirers, i decided that i didnt want to go to all the effort of cleaning out the exchanger, only to find the same problem recurring again. So i bit the bullet, and ordered a new secondary heat exchanger, plus new o rings.It took over 2 weeks to come.I changed it ,switched on, and all my problems were gone. None of the annoying misleding error codes either. All fixed

tony, November 2013

Thanks Kash, i concluded that as the secondary exchanger serves both dhw on one side, and central heating on the other, that as the ch is a sealed system, it wouldnt scaleup.The dhw side therefore might scale up just like the electric kettle does. The boiler is 6years old, and i live in a hard water area. Many thanks for your help tony

tony, October 2013

yes i would say your on the right track. just remove it and try hosing the blockages out. if no luck purchase some sentinel x800. boil some water, then pour it into a bucket. now put half the x800 into the bucket. put the heat exchanger in there and leave it for 5 mins. remove it and hose the heat exchanger through. if u have a jet wash u will get better results

kash, October 2013