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?
Rainwater harvesting and storage
Passive
One of 10 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 roof area and material suitable for potable-adjacent collection (avoid lead flashing, treated shakes)
Gutters and downpipes that lead rain from the roof into a storage tank. A simple diverter sends the first, dirtiest water of each shower away before the tank fills. It gives free water for the garden, washing and flushing, and drinking water once it is treated. The supply follows the rain.
Roof/gutter collection surface: matches roofing material lifespan; the tank itself per the elevated cistern/tank storage figure
Embodied carbon
Low
Space / material use
High
Output timing
Continuous process
Skill to repair
Basic
Regulation (FR example)
Non-potable water indoors is governed by decret 2024-796 and the arrete of 12 July 2024 (in force 1 September 2024, replacing the arrete of 21 August 2008). Permitted uses include toilet flushing, indoor floor washing and garden watering at building scale. Drinking, cooking and bathing are not permitted. A declaration to the mairie is required where the building is also connected to the public network.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Rainwater harvesting and storage (This page) 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: Occasional · Works without the grid: Yes Choose it if you have a roof and want free water for the garden, washing and flushing.
Drilled well with an electric pump 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: None · Works without the grid: No Choose it if there is water under your land and you want your own supply at the tap through dry spells.
Spring capture 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: None · Works without the grid: Yes Choose it if a spring rises on your land and you want water that can flow to you with no pump.
Drilled well with a hand pump Can I use it? Not 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 you have a well and want water through any power cut.
Drilled well with a rope pump Can I use it? Not 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 you have a well and want the cheapest hand pump, repairable with local materials.
Hydraulic ram pump (belier hydraulique) 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: None · Works without the grid: Yes Choose it if a stream with enough fall runs on your land and you want to lift water with no power, for decades.
Fog collector (cloud net) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Basic · Upkeep: Light · Change to daily life: Occasional · Works without the grid: Yes Choose it if you live where fog is frequent and want water with no power.
Mains water 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 network reaches you and you want treated water under pressure with nothing to manage.
Free-standing rainwater catchment 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 have no roof to collect from, or none clean enough for drinking water.
Spiral pump (coil pump) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: Regular · Change to daily life: None · Works without the grid: Yes Choose it if you have a moving stream without the fall a ram pump needs.
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.