sewer, n. — Green’s Dictionary of Slang

sewer n.

1. of an urban underground transit system [like a sewer it runs beneath the streets].

(a) the Metropolitan and Metropolitan District Railway.

1890–1904

(b) (US) the NYC subway.

1947

E. Condon We Called It Music 168: [W]e jumped in a subway—it was my first ride in a sewer—and went to visit Bix.

2. (drugs) the median cephalic vein in the arm, into which a drug is injected [play on shit n. (1a)/shit n. (5a)].

1942		Berrey & Van den Bark Amer. Thes. Sl.
1959		J.E. Schmidt Narcotics Lingo and Lore.
2001		ONDCP Street Terms 19: Sewer — Vein into which a drug is injected.

3. (Aus.) the mouth.

1969

J. Hibberd Dimboola (2000) 87: aggie. This is an outrage. horrie. Shut your sewer.

go into a sewer (v.) (also go into the sewer, hit the sewer)

(drugs) to inject a drug intravenously.

1937		B. Dai Opium Addiction in Chicago.
1938		D. Maurer ‘Lang. of the Und. Narcotic Addict’ Pt 2 in Lang. Und. (1981) 103/1: To go into the sewer. To take narcotics intravenously.
1950		Goldin et al. DAUL 98/1: Hit the sewer. To inject drugs hypo-dermically into the median cephalic vein.
1953		Anslinger & Tompkins Traffic In Narcotics 309: go into the sewer. To inject a drug into the vein.
1959		J.E. Schmidt Narcotics Lingo and Lore.
2001		ONDCP Street Terms 10: Go into a sewer — To inject a drug; inject in the vein.

go down the sewer (v.)

go into the sewer (v.)