sewer pipe
Refers to a pipe that carries sewage or wastewater, typically underground.
The sewer pipe got clogged and the water stopped draining.
Construction to lay new sewer pipes under the road has begun.
排水管 is a drainpipe or drainage pipe in general, not necessarily for sewage; 下水管 is specifically for wastewater/sewage.
Compound of 下水 (sewage, wastewater) and 管 (pipe, tube).