Cities Skylines – How to Manage Sewage Without Water Sources

You need constant growth without growth spurts. Your problem is likely related to growing to rapidly and, thereby, your population demanding services that become available with milestones without having the necessary funds to buy and support them.

Grow your city slowly, adding only a few residential zones at a time and focus first on breaking even and then generating a small profit. As long as your cims are employed they will remain in the city and generate some revenue.

At that point speed up your game time and accumulate some funds before expanding past the next milestone. Rinse and repeat until you have unlocked all basic categories relating to garbage disposal, crime, health, and education (fires don't seem to matter much).

If you're looking for temporary solutions, you can buy another square of land with more coast and move your water pump farther away from the drain pipe, or you can get all of your water from water towers instead.

Once your city is classified as a Big City by having 16,000 inhabitants, you will be able to build Water Treatment Plants, which purify water before dumping it into the ocean. They're more expensive than drain pipes, however, and can handle less water at a time.

Once you get rid of all the drain pipes, your bay should slowly return to being clean, sparkly, and just all around lovely. If you want to speed up this process, you can build some pumping stations to pull up contaminated water, without connecting them to your plumbing system. The nasty water will be pumped out of the bay and disappear, with nowhere to go.