The Basic Requirements

There are 6 basic requirements for a self-contained Green Warrant

Water Supply System - Fresh water storage of at least 12L per person in a ventilated, opaque, secure container.

Wastewater System - "Grey" water storage equal to (or monitored) your fresh water in a ventilated to the exterior, opaque secure container.

Fixed Toilet - A permanently installed toilet with a minimum of 3L per person useable inside the vehicle.

Sink - A sink that is available to wash hands and dishes and connected via a trap to your wastewater storage.

Rubbish Storage - A minimum 5L secure rubbish bin with a lid.

Ventilation System - Ventilation via windows, fan, or openable vents.

For more info check out the blog posts below or check the regulations via the links

The Regulations you need to comply with

The Government Legislation

This is the overarching government Act and outlines a lot of extra stuff for certifiers.

The Governmet Legislation - Secondary

This is the nuts and bolts of what I use to inspect and record everything I need to certify vehicles. Basically the checklist you can use to make sure you will pass your inspection.

Plumber, Gasfitters, Drainlayers Board Guidance

If your unsure about anything in the checklist this is where I'd go. A detailed guidance document with explanations and diagrams.