How To Stop Sewage Backing Up in Cities: Skylines

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In Cities: Skylines, sewage can get backed up if wastewater drainage facilities are not present, not operating, or insufficient in capacity.

Here’s a list of things to check so you can fix your sewage problem before people start leaving or getting sick:

 
This icon of a pipe spewing wastewater lets you know that sewage is backing up. / Cities: Skylines
This icon of a pipe spewing wastewater lets you know that sewage is backing up.
 

Task #1: Build a Drain Pipe

The first way drainage gets backed up is if there isn’t a wastewater drainage facility at all — either because the player forgot or didn’t know it was needed.

If you don’t have one yet, build one from the water menu.

 
Build a drain pipe on a body of water, downstream from your water intake pumps. / Cities: Skylines
Build a drain pipe on a body of water, downstream from your water intake pumps.
 

Make sure to place it downstream from your water intake pumps, or else the sewage it spews will contaminate the water supply and make your citizens sick!

 

Task #2: Make Sure Your Drain Facility is Connected & Working

Another common reason for backed up sewage is the drain facility not operating properly.

Your drain pipe needs electricity to function, so don’t forget to connect it to your power grid.

Also, be sure you’ve properly connected the drain pipe to your city’s water pipe system. A broken pipe icon will show up if it isn’t. It will also be grey, instead of cyan, when you’re looking at it in the water info view.

 
The drain pipe on the left is properly connected but the one on the right isn’t; the unconnected one is grayed out and has a broken pipe icon over it. / Cities: Skylines
The drain pipe on the left is properly connected but the one on the right isn’t; the unconnected one is grayed out and has a broken pipe icon over it.
 

Task #3: Check Sewage Capacity (And Build More Facilities if Needed)

If you’ve got working drain pipes but still have sewage backing up, your drain capacity might not be enough.

Click the water drop icon on the info views panel, or on the build menu, to bring up the water availability and sewage draining capacity info.

 
Here you can check the city’s water and sewage capacity, and current usage. / Cities: Skylines
Here you can check the city’s water and sewage capacity, and current usage.
 

Note that if you’d previously reduced your water and sewage budget to save on upkeep costs, this directly affects your sewage capacity. If this is the case, you might just need to raise your budget back up.

Otherwise, it’s time to build additional drain pipes to accommodate the demand.

Once your city gets larger, you can start looking at sewage facilities with larger capacity. The sewage buildings that come from DLCs have added benefits such as being less polluting or not needing to drain out into a body of water.

Building Milestone to Unlock DLC Cost (₡) Drain Capacity
(m3/week)
Notes
Drain Pipe Start N/A 2,500 120,000 Doesn’t require road access
Eco Water Outlet Start Green Cities 4,000 60,000 Doesn’t require road access
Produces less water pollution
Inland Water Treatment Plant Start Sunset Harbor 2,500 120,000 Requires road access; does not need a body of water to drain into.
Eco Inland Water Treatment Plant Start Sunset Harbor 4,000 60,000 Requires road access; does not need a body of water to drain into.
Produces ground pollution.
Fresh Water Outlet Tiny Town Natural Disasters 2,500 24,000 Doesn’t require road access
Water Treatment Plant Big City N/A 15,000 160,000 Doesn’t require road access
Eco Water Treatment Plant Capital City Green Cities 25,000 160,000 Doesn’t require road access
Produces less water pollution
Advanced Inland Water Treatment Plant Big City Sunset Harbor 15,000 160,000 Requires road access; does not need a body of water to drain into.
Produces ground pollution.
Eco Advanced Inland Water Treatment Plant Capital City Sunset Harbor 25,000 160,000 Requires road access; does not need a body of water to drain into.
Produces ground pollution.
 
The inland water treatment plant from the Sunset Harbor DLC does not need to be placed on a body of water / Cities: Skylines
The inland water treatment plant from the Sunset Harbor DLC does not need to be placed on a body of water
 
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Liz Villegas

Liz is a writer and photographer with a love for building and strategy games. Her spare time is often split between lifting, reading, drawing, annoying her dog Mr. Porky Butt, and squinting at stat tables on the wiki pages of whatever game she's currently playing.