Fluctuation has been evident for a while but thought it was us not moderating the heat properly - tried lots of ~"tricks" but nothing seems to work - but will ask the engineer about lime scale device because we have always had what seems like brown water coming from previous shower systems.
A year ago we replaced ancient boiler with new combi boiler - this seemed to work well but we then installed a steam cabin which we were assured the combi could more than cope with. The hot & cold water is difficult to regulate in the steam cabin - sometimes stone cold, sometimes red hot and to...