Blackwater, Greywater & Tiny Homes: What You Actually Need to Know

20 Feb

If there’s one topic guaranteed to raise eyebrows in tiny home conversations, it’s wastewater.
Blackwater. Greywater. Sewerage. Filters. Consents.

It sounds complicated — but it really doesn’t have to be.

At Ruru Tiny Homes, we deal with wastewater questions every single week, and the reality is this: there are several well-established, compliant, and practical solutions available for tiny homes in New Zealand. The right one simply depends on your site, your toilet choice, and your local council requirements.

Let’s break it down.

First Things First: What’s the Difference?

Greywater = wastewater from showers, basins, laundry, and sinks
Blackwater = wastewater from toilets, kitchen wastewater

They’re treated very differently — and for good reason.

Option 1: Connecting to an Existing Septic Tank

If your site already has a septic system, connecting a tiny home can be a very straightforward solution.

Typically, this involves:

designing the tiny home’s plumbing to align with the septic system
using quick-release couplings for easy connection and disconnection
ensuring capacity and system suitability

We always recommend engaging a licensed plumber with septic experience to ensure the system is compliant and correctly installed. This protects both the homeowner and the landowner — and avoids expensive problems later.

Option 2: Connecting to Public Sewerage

In more urban or semi-urban settings, connection to the public sewerage network may be possible.

This option:

requires building consent
must meet council and utility provider specifications
should always be completed by a licensed plumber

While it involves more paperwork, it offers a familiar, low-maintenance solution for those wanting a traditional wastewater setup in a tiny home.

Option 3: Treating & Reusing Greywater

Greywater systems are becoming increasingly popular — especially for off-grid or semi-rural sites.

Greywater Mate (via Allflow)

The Greywater Mate system provides an eco-friendly way to treat and reuse greywater for garden irrigation. It uses:

physical filtration
biological treatment
UV disinfection
grease trap options for kitchen water (Council depending)

This significantly reduces water wastage and supports a more sustainable lifestyle. As with any wastewater system, installation must meet local council requirements, and regular maintenance (filter cleaning and system checks) is essential.

GreyFlow™ Filtration Systems

For those wanting a high-performance, engineered solution, GreyFlow™ systems are an excellent option.

Available through WCTNZ® (NZ’s official GreyFlow™ agent), these systems:

provide powerful screening of problematic particulates
use high-reliability dripper systems for compliant land application
are fully WaterMarked
are designed by qualified hydraulic and wastewater engineers

GreyFlow™ systems have been proven across Australasia for over 20 years and were awarded the 2018 Australian Water Association Award for Innovation in Sustainable Water & Environmental Outcomes.

They’re available in scalable options — from standalone tiny homes to centralised systems for tiny home communities.

As always, local authority approval is required prior to installation.

Managing Blackwater in Tiny Homes

Blackwater (toilet and also kitchen, if not filtered through grease trap) management depends largely on your toilet choice.

Options include:

connecting a flush toilet to septic or public sewerage
using a holding tank with scheduled pump-outs
choosing waterless toilets such as composting or incinerating systems

Each option comes with different maintenance requirements, space considerations, and compliance pathways — and no single solution suits every site.

The Key Takeaway: There Is No “One Right Answer”

Wastewater systems for tiny homes are site-specific.

The right solution depends on:

zoning and council requirements
existing infrastructure
water supply
land use agreements
personal preferences

What matters most is choosing a system that is compliant, practical, and well-designed — and getting professional advice early.