Sand filter

Simple mechanical filtration stage, often paired with a wetland or as a standalone pretreatment. Gravity-fed and genuinely passive where the site gives enough fall; on flat ground or where flow has to rise, a pump is needed and it is no longer passive.

Cost
Low
Upkeep
Seasonal
Skill to build
Basic
Lifespan
10-20 years before media needs replacement (depends heavily on loading and pre-filtration upstream)
Embodied carbon
Low
Space / material use
Medium
Output timing
Continuous process
Skill to repair
Basic
Regulation (FR example)
On-site sanitation (assainissement non collectif): the installation must be declared to and approved by the local SPANC before work starts, and is subject to periodic inspection. Arrete du 7 septembre 2009 modifie.

Note: Cost, carbon and footprint are rated against the other options for this same need, not in absolute terms.

What your site needs

Enough fall from the source through the filter bed to run on gravity, otherwise a feed pump

Inputs

Outputs

Sources

What this page does not tell you

No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.