sewage lines in a city

I wonder how it is when I flush my toilet that whatever I flushed keeps going on to some destination other than right outside my house. It is hard to imagine that gravity is sufficient, after all not everyone lives on a hill. Are there pumps buried under ground that I never hear or know of? And about hills - there is one neighborhood near me that lies in the low spot between surrounding hills, how does the sewage waste get sent away?

Sometimes lift stations are used but most is just gravity. Those pipes can be a hunderd feet u/g when they reach the water treatment plant.

I happen to work for a wastewater utility, and I’ve learned that sewer lines are laid out to flow down hill as much as they can.

At local low points, lift stations are installed. A lift station is simply a place where water collects, and is pumped (lifted) to a higher level where it again can gravity flow towards the treatment plant.

Yep, we have pumps on the bottom of our major slopes. But we also have one line for gutter water & one line for sewer. Right now they are about to put in a $500,000 thingy to direct the gutter water into the sewer system so it won’t flow into the bay.

jordanthorn, some cities have sewer maps if you want to see a pipe layout.