Source screening
| Potential source | Planning evidence | Common concerns | Gate before reuse |
|---|---|---|---|
| Clothes washer | Measured volume per selected cycle, loads/week, products used | Salts, boron, bleach, lint, hot water, variable event volume | Appliance requirements, approved diversion, subsurface distribution and local source definition |
| Shower / bath | Measured flow, duration, bath volume and occupancy | Pathogens, hair, soaps, oils and warm wastewater | Allowed collection, exposure control, treatment/storage rule and maintenance access |
| Bathroom basin | Measured or observed daily use | Personal-care products, hair and pathogens | Local light-greywater definition and approved end use |
| Kitchen / dishwasher | Separate flow and composition evidence | Food, fats, oils, grease, detergents and higher organic load | Often treated differently or excluded; obtain explicit local confirmation |
| Toilet / urinal | Not included as greywater by these tools | Blackwater and high pathogen risk | Use the applicable wastewater system and authority requirements |
End-use screening
| Potential use | Quantity question | Safety / regulatory question |
|---|---|---|
| Subsurface landscape irrigation | Does seasonal plant demand and receiving capacity match each event? | Are the source, method, setbacks, crops, exposure controls and season allowed locally? |
| Laundry-to-landscape | Can whole outlets accept the measured appliance event? | Are appliance, valve, labeling, diversion and subsurface rules satisfied? |
| Toilet flushing | Do daily supply, peak demand and treatment/storage capacity match? | Requires explicit plumbing, cross-connection, treatment, disinfection and monitoring review; not covered by the sizing tools here. |
| Surface spray | Not evaluated | Exposure and aerosol risk; do not assume it is allowed. |
| Edible-crop irrigation | Not sufficient by itself | Crop-contact and local public-health rules must be checked explicitly. |
| Potable use | Outside scope | These tools never make wastewater safe to drink or design potable reuse. |
Evidence to keep with the plan
- Authority and rule checked, date and jurisdiction.
- Measured source volumes and event timing.
- Allowed end use, season, setbacks and diversion destination.
- Local ET, effective rainfall, plant factor and hydrozone area.
- Field infiltration evidence and receiving-basin dimensions.
- Products used, maintenance schedule and recommissioning observations.
Terminology varies. Greywater and graywater are spelling variants; legal definitions can differ materially. Never infer permission from the label alone.
Reference boundary. Do not convert an indicative value into a universal design, health or legal requirement. Check the cited source, laboratory context, certified claim and applicable jurisdiction.
Sources
- San Francisco Public Utilities Commission — Graywater Design Manual
- Washington State Department of Health — Greywater Reuse
- Australian Government — Australian Guidelines for Water Recycling
- U.S. EPA WaterSense — Water Budget Tool