Developed for simple, power-free greywater reuse, the GREYFLOW GRAVITY greywater diversion system is a compact, economical way to filter and distribute household greywater to a subsurface greywater field — without pumps, controllers, or electronics.

GREYFLOW GRAVITY OVERVIEW 

This practical, gravity-fed greywater system offers a straightforward solution for small dwellings and off-grid builds.

As Greywater Diverter

With the cost of water rising and many households wanting lower running costs, it makes sense not to discard usable water from showers and laundry. GREYFLOW GRAVITY is designed to divert and filter suitable greywater sources (typically shower, bathroom basin, and laundry) and deliver it by gravity to a subsurface irrigation / disposal field.

Because it’s gravity-fed, performance depends on good fall, a properly built dispersal area, and reasonable greywater volumes. It’s typically best suited to tiny homes and small households where there aren’t too many fixtures contributing at once. If your outflow volumes are high (multiple wet areas, heavy peak discharge, little fall on site), a pumped system may be more appropriate.

As a Drainage Pump Sump Station

GREYFLOW GRAVITY IS NOT A PUMP STATION. It does not include a sump pump or automatic lift.
If you need to move water uphill or out of a flooded area, use a dedicated GreyFlow™ pump station or an appropriate drainage pump solution.

✓ Gravity-fed (no pump)

✓ No controller required

✓ 100mm DWV inlet + outlet

✓ Compact and serviceable design

✓ Simple filter access

✓ Designed for subsurface greywater field distribution

✓ Ideal for tiny homes & off-grid sites 

GREYFLOW GRAVITY ADVANTAGES:

UNIT

Easy to integrate into standard drainage layouts with 100mm DWV connections
Simple, robust design with no electronics:

• Compact footprint and practical access for servicing
• Intended for gravity-fed installation (performance depends on fall and field design)

PUMP

• No pump included — gravity does the work
• Fewer moving parts = lower ongoing complexity
• If your site requires lift/transfer, choose a pumped GreyFlow system

FILTER

• Designed to reduce common greywater solids (lint / hair / debris) before the field
• Practical access for periodic cleaning
• Maintenance frequency depends on household use and products used (greywater chemistry matters)

DIVERSION

• Include a manual bypass/diverter so you can send greywater to sewer/approved disposal when needed (wet weather, maintenance, unsuitable loads)
• Works best when greywater is spread across multiple outlets in the dispersal area to prevent overloading one spot

BUILDING A GRAVITY GREYWATER FIELD (PRACTICAL NOTES)

A gravity system is only as good as the field it feeds. For best results:

• Keep continuous fall from the unit to the field (avoid dips where water can pool)
• Use a distribution point and a branched drain network so flow can be shared across the area and sections can “rest”
• Spread greywater into multiple subsurface outlets (mulch basins or infiltration trenches) rather than one discharge point
• Discharge below the soil surface and design the area so it never ponds
• Avoid spray irrigation, and avoid use near play areas or where people will contact the water
• Avoid using greywater on vegetables/salad crops
• Design with a bypass + overflow (and don’t store untreated greywater)

DOCUMENTATION, INSTALLATION & WARRANTY

• Greywater reuse systems should be installed and maintained appropriately for safe use.
• Check local authority requirements for setbacks and discharge limits, and whether consent is required.
• Warranty and documentation are supplied per WCTNZ® product terms for the GREYFLOW GRAVITY unit.

Note: generally not suitable for kitchen greywater without a grease trap installed inline (and a design that addresses fats/grease and higher contamination risk).
Detergent note: for long-term results, choose greywater-friendly detergents (low salt / low phosphorus) and avoid harsh cleaners.

WCTNZ® is the exclusive authorized distributor of GreyFlow™ greywater systems in New Zealand. All GreyFlow™ products available through WCTNZ® are guaranteed authentic, include official manufacturer warranties, and come with comprehensive local customer support—making us New Zealand’s trusted source for sustainable wastewater solutions.

Copyright © 2025 Waterless Composting Toilets NZ Limited (WCTNZ®). All short and long product descriptions and content are the property of WCTNZ® | Waterless Composting Toilets NZ. All rights reserved.

This content has been reviewed and approved by Dylan Timney, Managing Director of WCTNZ®, who brings over 17 years of composting toilet expertise and 16 years of experience in building and eco-construction in New Zealand.

Last reviewed: Jan 23, 2026