Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?
Mains sewer
Passive
One of 4 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
What your site needs
A public sewer reaching the property, and a connection permitted by the commune
Waste water from the house sent into the public sewer and treated at a works elsewhere. There is no tank, no field and nothing to maintain on the property. But if the network fails there is no fallback, and the nutrients in the waste are lost to the land.
Build it
This solution is not buildable as a DIY project.
Cost
Medium
Upkeep
None
Skill to build
Specialist
Lifespan
Connection and buried lateral: 50+ years; the public network beyond the boundary is the utility's responsibility, not the householder's
Embodied carbon
Low
Space / material use
Low
Output timing
Continuous process
Skill to repair
Specialist
Regulation (FR example)
Where a public sewer is available, connection is compulsory within two years of it being commissioned (art. L1331-1 code de la sante publique), and a connection charge applies. On-site sanitation is only permitted where no public sewer serves the property.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Mains sewer (This page) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Specialist · Upkeep: None · Change to daily life: None · Works without the grid: Yes Choose it if the house is on the public sewer and you want nothing to maintain.
Septic tank + drain field Can I use it? Not in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Light · Change to daily life: Occasional · Works without the grid: Yes Choose it if you are off the sewer and have a garden for a drain field.
Constructed wetland blackwater treatment Can I use it? Not in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Light · Change to daily life: Occasional · Works without the grid: Yes Choose it if you want all your wastewater treated on site by planted beds, with no power.
Aerobic treatment unit / micro-station d'epuration (package plant) Can I use it? Not in a flat · No rebuilding needed What does it cost me? Upfront cost: High · Skill to build: Specialist · Upkeep: Heavy · Change to daily life: Occasional · Works without the grid: No Choose it if your plot is small or wet, where a drain field would fail.
Sources
French public sanitation (assainissement collectif) connection practice
Limitations of this page
We don’t list sizing or quantities, as the yield of each technique depends on the quality of its build. The catalogue compares options but doesn’t dimension them. Regulatory notes are indicative, with a French example, and need to be confirmed locally.