D.C. Code § 2-137
The Inspector of Plumbing and his assistants shall be under the direction of said Mayor of the District of Columbia, and they are hereby empowered, accordingly, to inspect or cause to be inspected, all houses when in course of erection in said District, to see that the plumbing, drainage, and ventilation of sewers, and gas-fittings thereof conform to the regulations hereinbefore provided for; and also at any time, during reasonable hours, under like direction, on the application of the owner, or occupant, or the complaint under oath of any reputable citizen, to inspect or cause to be inspected any house in said District to examine the plumbing, drainage, and ventilation of sewers, and gas-fittings thereof, and generally to see that the regulations hereinbefore provided for are duly observed and enforced.
D.C. Code § 2-137