Greywater Basics FAQ

Greywater is household wastewater that has not come into direct contact with toilet waste. In practical terms, it commonly includes water from showers, baths, hand basins, laundries, washing machines, kitchen sinks, and dishwashers.

Toilet wastewater is not greywater. That is blackwater, and it sits in a different category with different management needs.

Yes. Kitchen wastewater is greywater, not blackwater. However, it is usually a heavier and more demanding form of greywater because it can carry higher grease, oil, food solids, and organic loading than lighter bathroom sources. It needs an appropriate treatment arrangement, not ordinary direct garden diversion.

Greywater is wastewater from non-toilet household sources. Blackwater is wastewater that contains toilet waste. The distinction matters because the reuse, discharge, and treatment requirements are not the same.

Yes, in the right situation. Greywater can sometimes support irrigation or controlled discharge outcomes, but reuse is not automatic. The wastewater source, site conditions, and system all matter.

Often yes, but only where the source of the water, the system type, and the site conditions suit that outcome. Suitable bathroom or laundry water may be diverted to a designed irrigation area. Kitchen-inclusive water needs a different treatment and reuse assessment.

Untreated greywater should not be casually stored for long periods. Once it sits too long, it can deteriorate, become more difficult to handle, and create odour or quality issues.

Short-term surge or collection stages are different. Those are controlled parts of system design, not long-term storage. Treated-water storage can also be part of a system designed for a specified reuse.

When greywater sits too long, solids can settle, odour can develop, and the water becomes less desirable to handle. That is why good greywater design usually focuses on prompt movement into the next stage of handling rather than simply holding it.

No. Not every greywater project needs the same level of system response. Some projects may suit simpler diversion-based arrangements, while others need more controlled treatment, especially where wastewater loading, kitchen inclusion, discharge sensitivity, or site constraints increase the demands on the system.

A Greywater Diversion Device (GDD) directs suitable greywater to a selected destination. A Greywater Treatment System (GTS) improves water quality before reuse or discharge. A GDD may also collect and transfer water to a GTS, so the two can work together.

Yes. In many projects, composting toilets and greywater systems are a logical pairing. The toilet changes or removes the toilet-waste stream, but the property still produces greywater from showers, basins, laundries, kitchens, and other fixtures.

Yes. A composting toilet may change the blackwater side of the project, but it does not remove the need to manage greywater properly. The remaining greywater still needs to be properly managed.

Start with the wastewater sources involved, the level of use, the intended reuse or discharge outcome, and the site conditions. A lightly used home may have different needs from a permanently occupied one, and commercial or shared-use sites may need a different arrangement. Building size alone does not decide the answer.

That is why WCTNZ® treats greywater as a project-by-project system question rather than a one-size-fits-all product choice.

Helpful starting details include:

• property type
• location
• expected use or occupancy
• wastewater sources involved
• site constraints already known
• what stage the project is at