A boiler is a closed vessel in which water or other fluid is heated.
The fluid does not necessarily boil.(In North America the term "furnace" is normally used if the purpose is not actually to boil the fluid.) The heated or vaporized fluid exits the boiler for use in various processes or heating applications,12 including water heating, central heating, boiler-based power generation, cooking, and sanitationŹródło: https://en.wikipedia.org/wiki/Boiler
As recently as the late 19th century sewerage systems in some parts of the rapidly industrializing United Kingdom were so inadequate that water-borne diseases such as cholera and typhoid remained a risk. From as early as 1535 there were efforts to stop polluting the River Thames in London.
Beginning with an Act passed that year that was to prohibit the dumping of excrement into the river.Leading up to the Industrial Revolution the River Thames was identified as being thick and black due to sewage, and it was even said that the river ?smells like death.?24 As Britain was the first country to industrialize, it was also the first to experience the disastrous consequences of major urbanisation and was the first to construct a modern sewerage system to mitigate the resultant unsanitary conditions.citation needed During the early 19th century, the River Thames was effectively an open sewer, leading to frequent outbreaks of cholera epidemics. Proposals to modernise the sewerage system had been made during 1856, but were neglected due to lack of funds.