What is the covered opening that gives workers access to a sewer?
AnswerA manhole
Manholes let crews enter and inspect sewers; their round covers cannot fall through the opening.
Science · Facts & stats
Sewer facts & stats
8 fact-checked facts about sewers and wastewater, each with the reason behind it. 4 more are in today's round and join this page after it closes.
The basics
What mainly flows into street storm drains?
AnswerRainwater runoff
Storm drains are built to carry away rain and melting snow from streets.
Going deeper
The Cloaca Maxima was an ancient sewer in which city?
AnswerRome
The Cloaca Maxima, one of the world's earliest large sewers, drained parts of ancient Rome.
Which engineer designed London's major sewer network after the 'Great Stink' of 1858?
AnswerJoseph Bazalgette
Joseph Bazalgette's intercepting sewers helped end London's cholera epidemics.
What is the purpose of the U-shaped trap under a sink?
AnswerIt holds water that blocks sewer gases
The water sitting in the trap acts as a seal, keeping sewer gas out of your home.
Sewer gas's rotten-egg smell comes mainly from which gas?
AnswerHydrogen sulfide
Hydrogen sulfide, made as bacteria break down waste without oxygen, smells like rotten eggs.
Expert level
In 1854, physician John Snow traced a London cholera outbreak to what?
AnswerA contaminated public water pump
Snow mapped cases around the Broad Street pump, helping show cholera spread through water.
A sewer that carries both stormwater and household wastewater in the same pipe is called what?
AnswerA combined sewer
Combined sewers carry both flows, which can overflow in heavy rain; separate systems use two pipes.
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