Early fire pumps
Towards the end of the eighteenth century manual fire pumps came into use which consisted of a pair of force pumps connected to a long handle and worked by a team of four men. Both pumps fed alternately into a chamber with a compressed air space similar to that described above. At the moment of change-over of feed from one pump to the other the compressed air expanded, and so maintained a steady flow of water to the hoses (Fig. 11.4).