Specifying greywater for Perth’s new southern suburbs

Perth’s southern growth corridor is where the realities of new suburban housing meet the region’s scarce summer rainfall. Across the City of Canning, City of Gosnells and new Perth Hills estates, two-storey family homes are being designed around larger backyards, multiple bathrooms and alfresco areas. That combination creates steady household wastewater and predictable irrigation demand. A well-specified greywater system can connect the two, reducing pressure on reticulated water while giving designers something tangible to explain to purchasers.

The ins and outs of specifying greywater recycling in new suburban homes south of the River are mostly about coordination rather than exotic equipment. Greywater generally comes from showers, baths, washbasins and laundry equipment, but permitted sources and treatment levels differ. It must remain physically separate from drinking water. Unlike a rainwater tank, which stores one roof-fed stream, a greywater system responds to what people do at home, so the architectural brief, landscape plan, plumbing details and operating model need to agree from the first drawing.

Start with the site’s water and waste

Perth’s climate gives greywater a strong seasonal argument. Most rain falls from May to September, while summer is hot and dry; Water Corporation watering rosters and sprinkler restrictions therefore shape how a new garden consumes water. A household still generates greywater throughout the year, including during the driest weeks, so matching that supply to irrigation can be valuable. The design team should also record rainfall capture, roof area, any existing tanks and the watering schedule so that greywater is not credited with demand the landscape cannot actually use.

Begin with the site rather than a product. A typical new block may have a compact front garden, a substantial rear lawn and a covered outdoor room, but the landscape can alter that balance quickly. Test whether the proposed planting will need irrigation at all, and in which months. Check where the house sits relative to boundaries, mains, neighbouring structures and service trenches, since access to tanks and treatment equipment affects both appearance and maintenance. On larger developments, calculate demand and waste generation across apartments, common amenities and landscaping instead of applying a single household assumption.

Everyday household behaviour will determine whether the system works after handover. Family showers, washing-machine cycles and bathroom use create a different flow profile from that of an empty holiday house. New estates often welcome young families, but occupiers change, tenants move on and teenagers alter bathroom routines. Record who will use the dwelling, whether laundry is in the main house, and how long residents are away. A modest system with adequate storage can be more reliable than a large unit that is oversized for a quiet street.

Match the system to household use

There are several routes, from approved diversion for landscape use to packaged treatment that can supply water for a toilet or other permitted non-potable fixtures. A detached home with a straightforward yard may need only a compact treatment unit, collection tank and pump, while a family bathroom with a WC in the same room can support a toilet-retrofit arrangement. Multi-dwelling developments often need a shared treatment plant and a coordinated pipe network. The important choice is the end use: each additional treatment step brings cost, maintenance and regulatory scrutiny, so it should earn its place.

The local market includes specialist greywater distributors, irrigation suppliers and licensed plumbing contractors, with a mixture of Australian-made equipment and imported systems. Buyers should compare local installation experience, warranty coverage and the availability of replacement cartridges or membranes, not just purchase price and daily treatment figures. Salt-laden coastal conditions, Perth’s dust and hard water can affect components differently, and a product that is easy to service locally will usually prove more useful than one with marginal theoretical efficiency. The Contemporary program extends this kind of discussion across architecture, interiors and design events, including Contemporary Wine In Design.

Specify the complete assembly, not just the treatment box. Collection pipes need a suitable slope, tanks need enough volume to ride through low-use periods, and pumps require a reliable power supply, isolation valves and an approved overflow path. Filtration must be accessible without digging up the garden, while alarms and clear service zones help owners respond to faults. Also consider odour, pump noise and condensation where equipment sits near bedrooms or covered terraces. A small architectural adjustment early in the project can prevent an intrusive cabinet or noisy enclosure later.

Get approvals and plumbing details right

In Western Australia, greywater work sits within building and plumbing controls, including the Building Act 2011 and requirements administered through the WA Building Commission. The current AS/NZS 1710.3 code for tertiary pipework is central for recycled-water installations, alongside general plumbing standards and manufacturer-specific approval conditions. A Water Corporation requirement may apply to particular systems or developments, and local government or health requirements can affect the proposed use. Responsibility must be allocated early: a licensed plumber can design compliant pipework, but the architect or builder remains responsible for coordinating the approval package.

The hydraulic drawing needs to prove that waste and potable water cannot mix. Clearly identify greywater and reclaimed-water pipes, show their routes through the slab and walls, and include the required isolation devices, backflow protection, venting, pressure controls and access points. The layout should keep greywater away from food preparation, and kitchen wastewater should remain excluded unless a specific approved system includes it. Avoid joining a storage tank directly to a drinking-water line without the prescribed break and backflow arrangement. Tank covers need safe access, and any pump or electrical equipment near water must suit the wet location.

Set an approval matrix before tender rather than appointing a supplier and working backwards. For one dwelling, the pathway may involve a building permit, plumbing certification and a certified greywater installer; for an estate, it can add Water Corporation conditions, hydraulic modelling and council health review. Give the tender documents a coordinated specification that names the source fixtures, treatment performance, tank and pump requirements, pipe sizes, controls, overflow, commissioning tests and maintenance tasks. Require the nominated installer to submit product certification and details of local service support. This prevents an imported appliance from being approved for installation while leaving the wider building design dependent on assumptions.

Coordinate the garden and future services

The landscape determines how often the system will be used and whether it can achieve a credible water saving. Specify pressure-compensating drip lines or other suitable irrigation in zones that reflect plant needs, and avoid broad sprays that waste water or create aerosols. An approved controller can irrigate in the early morning and use soil moisture or rain information to skip unsuitable cycles. Restrict uses to those permitted for the system: greywater is not suitable for drinking, food preparation or contact with edible crops, and application method matters for health. Indigenous and climate-adapted planting can reduce demand, but a new suburban garden may still benefit from targeted reuse.

Greywater should also be planned alongside rainwater, hot water, solar power and future charging or storage services. Keep collection pipes away from structural footings, garden trees and future deck work, and leave access to filters, tanks and valves. A combined non-potable network may be sensible when a development already uses recycled mains water or shared rainwater storage, but each source needs its own treatment and control. Recording these relationships in the architectural documentation protects resale value and gives owners an intelligible system rather than a set of disconnected boxes.

Australian experience varies sharply by city. Sydney has established recycled-water infrastructure for non-potable purposes, while Melbourne and other capitals approach water reuse through different planning and plumbing frameworks; Brisbane’s summer rainfall creates another operating pattern. Western Australia cannot copy a Sydney connection or assume approval from another state, yet the national market is increasingly selling homes with heat pumps, rooftop solar, batteries and smart controls as one efficiency package. The Australian Institute of Architects WA Chapter’s upcoming talks program offers a useful setting for architects and students to examine those systems and the standards behind them.

Make the decision before the slab is poured

Treat greywater as a coordinated building system with a commissioning plan, not as a late appliance. Decide the fixture sources, treatment route and end use while the floor plan is adjustable. Carry the system through architectural, plumbing and landscape drawings, then include tank capacity, pump location, pipe routes, isolation points and controls in the tender schedule. Define measurable tests for leakage, flow, diversion and safe shutoff, and require the installer to demonstrate them with the owner or builder present. A performance record at handover is more valuable than a polished product brochure.

A plain-language handover turns technical compliance into everyday performance. Provide an owner’s manual, labelled shutoffs, service intervals, filter stock details, warranty contacts and the name of a competent local contractor. Show residents how to reset alarms, clean screens and understand which fixtures contribute waste. For tenanted or short-stay properties, make sure the property manager can repeat that briefing whenever the occupant changes. A nearby replacement part and a direct phone number can be the difference between a minor service and an abandoned system.

Brief the whole project team now, before site works lock in the layout. Decide whether greywater will support irrigation, a toilet or both, appoint the licensed installer, and place approval obligations in the consultant schedule. Ask for a coordinated specification and a maintenance budget, then carry those commitments through completion. That early decision can turn greywater from a promising sustainability claim into a quiet, useful service that works for the families and gardens of Perth’s southern suburbs.