Abstract: A dry pipe sprinkler system comprises at least one sprinkler head (18); a control valve (10) operable to supply an extinguishant to the sprinkler head; a system of pipes (16) interconnecting the control valve and the sprinkler head, the pipe system comprising a control column (26) and a riser pipe (42); and a pressure control means (38) located downstream of the control valve and upstream of the sprinkler head; wherein the pipe system is arranged to form a manometer which contains a quantity of extinguishant up to a predetermined level (48) in the control column and in the riser pipe; wherein the manometer is arranged such that the creation of a pressure differential across the pressure control means results in a reduction in the extinguishant level in the control column and a rise in the extinguishant level in the riser pipe; and wherein the control valve is adapted to open to supply extinguishant to the sprinkler head when there is a change in the predetermined level of extinguishant in the control column a