The tundish is a trickling lantern valve
once ignored, now a vital sign
as a city of pipes holds its breath,
air stacks compressing as water
expands to fill the cylinder tower.
One lock releases, another blocks.
Aim your phone at the hidden underside
and answers appear in the camera flash
etched on silver labels, beam them
to the engineer, who sets de-
fibrillators kicking at the
heart of the house. To maintain this
balance of air and water you
must first recharge the system, then
allow it slowly to exhale.