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?

Treatment / filtration

Cleaning greywater enough for whatever comes next. Soap, grease and food scraps are what have to go. The options differ in how clean the water ends up, whether the treatment runs on plants and gravity or on a powered machine, and how much room each one takes.

Ranked by effluent quality, how clean the water is at the outlet, and how consistently. Membrane filtration is the ceiling and the only option producing water fit for indoor non-potable reuse; the biological beds reach a good standard given enough area and residence time; a sand filter alone is a pretreatment stage, not full treatment. Drain water heat recovery appears in this sub-function but is not ranked. It recovers heat and does not treat the water at all.

Solutions

• Constructed wetland / reed bed filtration: A bed of gravel planted with reeds, which the used water from sinks and showers flows through. Bacteria living on the gravel and roots feed on the dirt and clea
• Sand filter: A tank or bed of sand that used water trickles down through. The sand holds back particles and the life that grows in it cleans the water further, either on its
• Greywater heat recovery (drain water heat exchanger): A pipe wrapped around the shower or sink drain, carrying the cold water on its way to the water heater. The warm water going down the drain passes its heat to t
• Membrane bioreactor (MBR) greywater recycling package unit: A packaged machine that cleans the used water from sinks and showers with bacteria and then a fine membrane filter. The water that comes out is clean enough to
• Wood-chip filter (Filtres a Broyat de Bois, FBB): A bed of wood chips that the used water from sinks and showers trickles through. Microbes living on the chips feed on the dirt and clean the water. It works wit