turncock

From turn +‎ cock.

turncock (plural turncocks)

1. A tap or faucet that regulates the flow of a fluid.
2. A person employed to turn on the water for the mains, to regulate the fireplugs, etc. for a water company.
   • 1851, Henry Mayhew, “Costermongers”, in London Labour and the London Poor:

     1,000 crossing-sweepers; another thousand chimney-sweeps, and the same number of turncocks and lamp-lighters;