Well well I wash my dishes in hot water, not boiling hot ofc, but I feel safer that way considering I have bacteria phobie I always wash and clean stuff with the temperature I need which can kill bacterias and any other nastyass things. I just don't like cold water, tho cold water can help, when you really have no other option, like, as you mentioned, your brokenass boiler or whatever it is called. So shouldn't be a issue to clean it temporarily with cold water. Tho I personally prefer hot water.