Source
https://www.branz.co.nz/pubs/research-reports/sr159/ — original source (opens in a new tab; the file is not redistributed)
Context: ni · Feeds D03 (household water demand, potable vs non-potable split)
Summary
BRANZ SR159 is the classic New Zealand per-fixture residential water end-use study: 12 Kāpiti Coast homes monitored over separate winter and summer periods at 10-second resolution, with Trace Wizard disaggregating flow into end uses. It supplies the per-fixture breakdown the national SR469 study (OT_036) measured total demand for but did not itself resolve. For the water-domain redesign it lets household demand be split into a potable share (drinking, cooking, bathroom, hand basin) and a non-potable share (toilet, laundry, outdoor).
Key claims
- claim: "NZ residential water end-use by fixture (12 Kāpiti homes; average litres/person/day, winter / summer): Shower 44.9 / 45.3; Washing machine 39.9 / 41.8; Toilet 31.3 / 35.5; Tap 22.7 / 24.3; Bathtub 5.5 / 3.1; Dishwasher 2.1 / 2.7; Outdoor 13.9 / 44.2; Leaks 7.0 / 6.7; TOTAL 168.1 / 203.9. As a share of total WINTER use: Shower 26.7%, Washing machine 23.7%, Toilet 18.6%, Tap 13.5%, Outdoor 8.3%, Bathtub 3.3%, Dishwasher 1.2%. [verified verbatim against Table 9 and the winter pie Figure 20]"
source_location: "§8.2 Table 9 'Summer/winter end uses comparison' (p.35); cross-checked against Figure 20 winter total end uses (p.17)."
- claim: "Indoor use dominates in winter (~88% of total, 147 L/p/d) with a small outdoor/garden component (8.3%); in summer outdoor rises to 21.7% (44 L/p/d) while indoor use is near-constant, so the entire seasonal increase in demand is outdoor. [verified verbatim against Table 9 indoor/outdoor totals]"
source_location: "§8.2 Table 9 (p.35), TOTAL INDOOR vs Outdoor rows."Model use
- Resolves RT_408. Splitting the fixtures per the modeling definition (potable = Tap + Shower + Bathtub + Dishwasher; non-potable = Toilet + Washing machine + Outdoor; leaks/misc unclassified) gives a derived rollup:
- Potable ≈ 75 L/p/d, near-constant year-round; non-potable ≈ 85 (winter) to 121 (summer) L/p/d.
- Headline split ≈ 40% potable / 55% non-potable annualised (winter ~45/51, summer ~37/60) OT_227. (This is a derived figure, not a source claim; the arithmetic is stated so the assumption is explicit.)
- This inverts the interim 60/40 potable-heavy placeholder — real NZ data makes non-potable the larger share, so greywater/rainwater can legitimately offset more of household demand.
- Definition sensitivity (~30 points): under strict dual-reticulation (only drinking + cooking on mains; shower/bath/WC/laundry/garden served from the non-potable tank, as at Earthsong), potable collapses to ~15% and non-potable rises to ~85%, matching the “~83% non-potable” already carried from LIT_007. The model must state which definition it adopts.
Research targets
No new research targets. Resolves RT_408 (NZ residential potable/non-potable end-use split).
Connections
Links to
EDT domains (1): D03: Water, Waste & Circular Systems
Referenced by
Sources (1): OT_036