Okay, obscure pet peeve time, since a lot of stories I’ve read – both professional and fan-written – get this one wrong:
A sanitary sewer is where stuff you pour down the sink or flush down the toilet goes. It has predictable, constant flow, a closed structure, and is typically not human-accessible without excavation unless it’s combined with or routed through a storm sewer (see below).
A storm sewer is where stuff that goes down the drains and gutters in the streets ends up. It has irregular flow (to the point that it may be completely dry for portions of the year, depending on the climate), a non-closed structure that may incorporate open watercourses (e.g., creeks and streams) as portions of its network, and – owing to the need to provide adequate surge capacity during periods of high precipitation – may have main tunnels that are large enough to walk upright in.
In most cities with well-developed infrastructure, these two sewer networks are entirely separate. The pipes that comprise the sanitary sewer may be routed through portions of the tunnels that comprise the storm sewer for ease of access, and breakages or overflow in the sanitary sewer network may result in waste being periodically dumped into the storm sewer, but in general, the kind of sewer you can walk in will have you wading through rainwater, not waste.
Certainly, this doesn’t mean storm sewers are clean – you’ve seen the sorts of things people dump in the streets! – but it does mean your protagonists aren’t necessarily going to get covered in shit just from walking through a sewer.
jacobvanloon
gummygunk
titsay
izzy806
vaporwave
turnnoffyourmind
