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?
Reverse osmosis (RO) filtration
Needs the grid
One of 5 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
A unit that forces water under pressure through a very fine membrane that lets water pass but holds back salts, metals, nitrates and other dissolved pollutants. It gives the purest drinking water of any home system. But it uses a lot of electricity and wastes several litres for each litre made. Its membrane has to be replaced by a professional.
Build it
This solution is not buildable as a DIY project.
Cost
High
Upkeep
Seasonal
Skill to build
Specialist
Lifespan
System/housing: 10-15 years; the membrane itself needs replacement every 2-5 years
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Reverse osmosis (RO) filtration (This page) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: High · Skill to build: Specialist · Upkeep: Heavy · Change to daily life: None · Works without the grid: No Choose it if your water carries nitrates, metals or salts and you want the purest drinking water.
Multi-stage filtration + UV disinfection Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Heavy · Change to daily life: None · Works without the grid: No Choose it if you want the whole house on safe drinking water from rain or raw water.
Bio-sand filter Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Regular · Change to daily life: Daily · Works without the grid: Yes Choose it if you want safe drinking water with no electricity, from a filter you can build.
Ceramic candle filter (silver-impregnated) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Regular · Change to daily life: Daily · Works without the grid: Yes Choose it if you want drinking water with no power from a pot on the counter, with nothing to build.
Solar still (solar distillation) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: Daily · Works without the grid: Yes Choose it if your only source is salty or badly polluted and you have sun.
Sources
Water treatment industry comparison sites (APEC Water, Culligan, et al.)
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.