Source
https://www.branz.co.nz/design-build/publications/bu665-residential-greywater-systems — original source (opens in a new tab; the file is not redistributed)
Summary
BRANZ Bulletin 665 (2021) is the NZ design-and-compliance guide for residential greywater reuse — collecting the wastewater from baths, showers, basins and (sometimes) laundry, and reusing it for subsurface garden irrigation or, when treated, toilet flushing. It is the demand-reduction companion to rainwater harvesting: a typical household produces 100–200 L of greywater per day, a large fraction of total household water that can offset potable use. The bulletin is design and regulatory in focus (treatment levels, the 24-hour untreated-storage limit, consent pathways) and carries no cost data. Its value for Neobiome Intelligence is the NZ greywater volume figure, the treatment/health rules, and the consent constraints — the basis for the greywater_recycling technology page.
Key claims
- claim: "Greywater is the wastewater from laundry tubs, bathroom basins, showers and baths (and sometimes washing machines). The wastewater from kitchen sinks and dishwashers is NOT collected as greywater. Greywater must never be used as a potable source, or for washing, bathing or swimming."
source_location: "§1.0.1–1.0.3; §3 (p.1, p.4)"
- claim: "The volume of greywater produced by a typical household is 100–200 litres per day (variable)."
source_location: "§ design considerations (p.4, 'amount and source of greywater')"
- claim: "Untreated greywater can be reused only for subsurface garden irrigation and must be used immediately or within 24 hours — it should not be stored any longer (untreated, ponded greywater can contaminate soil). Treated greywater (filtered to remove solids such as lint and hair, then disinfected physically or chemically) can be stored and used indoors for flushing toilets."
source_location: "§1.0.2, §3.0.x (p.1, pp.4–5)"
- claim: "Greywater systems require a building consent, granted as an Alternative Solution (there is no Acceptable Solution for greywater reuse); a resource consent may also be needed to discharge greywater to land. Council policies vary — some promote reuse, some restrict certain greywater types, some have no policy — and no single piece of NZ legislation covers greywater reuse end to end."
source_location: "§2.0.3–2.0.5 (p.2)"
- claim: "Greywater plumbing must meet AS/NZS 3500.2:2021 (Plumbing and drainage – Sanitary); non-potable greywater pipework and outlets must be clearly labelled as non-potable per AS/NZS 3500.1; AS/NZS 3500.2 §7.4 requires the treatment device of a greywater system to be marked."
source_location: "§2.1.1, §3.0.11 (p.2, p.5)"
- claim: "Benefits of greywater reuse include reduced demand on mains/potable supply, saving rainwater-tank water for other uses, reduced wastewater discharge, and increased resilience during drought and water restrictions."
source_location: "§1.0.4 (p.1)"Neobiome Intelligence relevance
- D03 — demand-reduction water stream + new technology. At 100–200 L/day per household, greywater is roughly 20–45% of NZ household water demand (vs the ~435–504 L/day household figure from OT_036) — a significant reuse stream that, with rainwater, reduces potable demand. This grounds in NZ design/regulatory terms the demand-side reuse the wiki documents from overseas (the Gullberg Swedish study found greywater recycling alone supplies ~71% of community freshwater self-sufficiency, LIT_022) OT_040. Seeds the greywater_recycling technology page.
- D03 — regulatory constraint. Greywater reuse needs a building consent as an Alternative Solution (no Acceptable Solution) plus possible resource consent for land discharge — a heavier consent pathway than rainwater, and a real barrier for a community design to plan for (parallels the on-site-wastewater consent refusal int_006 described at Earthsong) OT_040.
- ⚠ Scope: no cost data (design guide) — greywater system capex is a gap (new RT).
Research targets
Research gaps
- NZ installed cost of residential/community greywater diversion vs treatment systems (filter + disinfection) — Bulletin 665 has none; needed before greywater can be costed in the model’s water domain (parallels the rainwater capex in CR_016).
- The achievable greywater reuse fraction at community scale in NZ (how much of the 100–200 L/day can realistically offset irrigation + toilet demand year-round), to size the demand reduction.
Connections
Links to
Technologies (1): Greywater Recycling
Referenced by
Sources (5): OT_124 · OT_129 · OT_135 · OT_228 · OT_229
EDT domains (1): D03: Water, Waste & Circular Systems
Technologies (1): Greywater Recycling