Irrigation 3 — Turning hydrozones into stations

Never mix lawn and garden beds, or sun and shade, on one station. Divide the garden by water need, plant type and aspect, then check each station fits inside your available flow and your legal watering window.

⏱ 90 minAdvanced💧 Irrigation mini-course🔗 11 resources (10 free)

A hydrozone is an area of planting that wants the same amount of water, at the same frequency, under the same conditions. A station is the group of emitters one solenoid valve switches on together. This lesson makes those two line up, then proves the result survives two limits you have already measured: how much water your block delivers at once, and how long the law lets you run.

Josh Byrne’s landscaping FAQ for his own house in Hilton defines hydrozoning as “grouping plants based on their common water and management requirements” so that “various hydrozones can be serviced by different irrigation stations”. On one suburban block he runs seven, each with its own emitter type and its own station.

You are renovating, so you have inherited a station layout someone else drew, usually to suit the pipe on the truck. Assume it is wrong until your plan says otherwise.

What a professional does at this stage

Two rules and two tests, in that order. Everything else is detail.

Rule 1: one station contains exactly one hydrozone and exactly one emitter type. No exceptions, no “it’s only a small bed”.

Rule 2: one hydrozone may need several stations. Flow can split a hydrozone across two valves. Flow is never a reason to merge two hydrozones onto one.

Get those the wrong way round and you produce the commonest fault on Perth blocks: a front station with pop-up sprays doing the lawn and the shrub bed behind it. The lawn wants about 10 mm twice a week into the top 150 mm; the shrubs want a deeper soak far less often. One of them is always being punished — usually the shrubs, watered onto their foliage at lawn frequency while the lawn looks fine.

Hydrozones get drawn before any pipe, because station boundaries set valve positions, valve positions set the mainline route, and the mainline route sets the trenching. Redrawing them on paper costs ten minutes; redrawing them with the trench open costs a day.

What makes two areas different enough to need separate stations

Any one of these is sufficient on its own.

Difference	Why it forces a split
Lawn versus bed	Root depth 100–150 mm versus 300–600 mm, different emitter, different frequency. Never combine.
Sun versus shade	A west-facing bed against brick or limestone can want 40–50% more water in February than the same plants on the shaded south side.
Emitter type	Spray applies 35–45 mm/hour, rotary 10–15. On one valve, one is always wrong.
Water need rating	Established natives, thirsty exotics and a vegetable bed are three hydrozones even where they touch.
Slope and soil	A verge falling to the road, or a bed on shallow sand over limestone, drains faster than flat improved soil.
Containers	Dry out several times faster than ground beds. Separate station, or hand water.
New planting	Needs its own frequency for its first summer. Give it a station or a separate program.

Aspect is the one people skip, and in Perth it is the expensive one. Afternoon sun from November to February plus radiant heat off a limestone wall or a colorbond fence is a different climate from the south side of the same house. If one bed has always struggled while the identical bed opposite thrives, check the station numbers before you blame the plants.

Test 1: does each station fit inside your available flow?

From Irrigation 2 you have a measured flow. Set a design flow at about 80% of it and never exceed it on any single station.

The arithmetic, using published spray flows of roughly 2.3 L/min for a 90 degree arc, 4.5 for 180 and 9.1 for 360:

Design flow 24 L/min
Proposed lawn station: 4 × 90° (9.2) + 2 × 180° (9.0) + 2 × 360° (18.2) = 36.4 L/min
Over by 12.4 L/min, so this hydrozone becomes two stations of 18.2 L/min each

Note what did not happen: nothing got added to the second station to “use up” the spare capacity. Spare capacity is free; a mixed station is not.

Overloading a station does not announce itself by failing. It shows up as heads misting instead of throwing and a dry arc on one side of the lawn, which people then fix with more run time, which drowns everything else. Irrigation 1 covers why.

Test 2: does the whole thing fit inside the watering window?

This is the constraint that catches people, and it is a legal one.

Perth and Mandurah are on a two-day-per-week roster, and you may water once on a rostered day, either before 9am or after 6pm (DWER). One window, not two, and bore users are on the same roster. Breaches attract a $100 on-the-spot fine, and a controller malfunction is not a defence.

So: every station scheduled on a given day must finish inside one window. Legally the morning window opens at midnight, but design to roughly 4:30am to 9:00am — about 270 minutes — so watering ends near dawn and foliage is not wet all night.

An example on a modest block, using the Water Corporation application rates:

Station	Hydrozone	Emitter	Run time
1	Rear lawn (west half)	Rotary	50 min
2	Rear lawn (east half)	Rotary	50 min
3	North beds, full sun	Dripline	35 min
4	South beds, shaded	Dripline	30 min
5	Verge, full sun	Rotary	45 min
6	Pots and planters	Drippers	10 min
		Total	220 min

Start at 5:20am and that finishes at 9:00am exactly — too tight, for the reason everyone forgets. Seasonal adjustment multiplies every run time. Set the controller to 120% in February and 220 minutes becomes 264. Design the window against your peak-summer setting, not your mild-month one.

Three ways to buy back time, in order of preference:

Do not run every station on every rostered day. Established natives may need one watering a fortnight in summer, not two a week. Put them on a second program on the alternate day. Your peak day is the day two programs coincide, so make sure they never do.
Change the emitter, not the schedule. A rotary station at 12 mm/hour takes 50 minutes for 10 mm; spray at 40 mm/hour takes 15 — but sprays lose far more to wind and evaporation here. See Irrigation 4.
Reduce irrigated area. Mulch, paving and dry gravel need no station.

One nuance in your favour: cycle-and-soak costs little extra elapsed time once you have six or more stations, because station 1 soaks while stations 2 to 6 run. On a two-station system it adds dead time you cannot afford — Irrigation 5.

Renovating: when to re-valve rather than reuse

Overlay your new hydrozone plan on the station map from your existing garden audit, then apply one test: does any existing station boundary cross a hydrozone boundary? If it does, that station gets re-valved. Do not try to save it with clever nozzle selection or a shorter run time — you cannot schedule your way out of a mixed station.

You may legally run each station for two minutes to test it, on rostered days, before 9am or after 6pm. To map a large system in winter during the switch-off, a Waterwise Garden Irrigator may test outside those windows.

Three points that decide the budget:

A solenoid, a valve box and a length of poly are among the cheapest items in the whole build. Replacing plants that were on the wrong station is not.
Existing mainline and trench routes are often reusable when the station layout is not. Reuse the corridor, re-cut the boundaries.
Count your controller stations before you finish the plan. Domestic controllers come in 4, 6, 8 and 12 station sizes; if you need nine, buy the twelve. Name each one now — “S3 north beds, sun, dripline” — because that list becomes the controller labels and the as-built in Irrigation 8.

New planting, the exemption and the winter ban

New plants cannot be established on a two-day roster. Apply for a watering exemption before you plant. It covers new gardens and new lawn including roll-on, runners, shredded lawn and seed, and runs up to 42 days from planting between 1 October and 31 March, or 35 days between 1 April and 30 September. The published schedule starts at 3.5 mm three times a day and tapers — three separate start times, so check the establishment program still fits the window. Watering outside the conditions of an exemption risks a $500 fine.

The other date to design around: the Sprinkler Switch-off, 1 June to 31 August every year, bore water included. If the build finishes in May, new turf is hand-watered through winter or you apply for an exemption — see turf for Perth.

Safety

Nothing here is physically dangerous, but two things downstream are. The mains supply to a controller and any backflow device on the scheme connection are trade work, not weekend work — see Irrigation 6 and Irrigation 7. Before any trench is cut for a new valve, locating services applies again.

What happens next

You should now have a numbered station list: for each one, the hydrozone it serves, its aspect, area, emitter type, total flow and provisional run time.

Irrigation 4 takes that list and picks the actual emitter for each station — where matched precipitation rate, nozzle selection and pressure-compensating drip turn station boundaries into a parts list.

Checklist

Every station contains one hydrozone and one emitter type
Station flow totals stay within your measured available flow
Total run time for all stations fits the legal watering window
Sun and shade areas are on separate stations

Where to go deeper

Every link below was fetched and checked before it shipped. Nothing here is a guess.

Freegovernment5 minPerth / WA
Check your watering days
Water Corporation
Why this oneEnter your street number and postcode and it returns your actual rostered days, which are allocated by the last digit of your address rather than by suburb. It also states the rule this whole lesson is built around — "Only water once before 9am or after 6pm on your rostered watering days" — confirms that garden bore users in Perth and Mandurah are on the same roster and times as scheme users, and notes that $100 on-the-spot fines are issued for breaches with inspectors operating seven days a week. It adds the detail that catches people out: a controller malfunction is not a defence.
Link checked 2 Aug 2026
Freecalculator5 minPerth / WA
How long should I run my sprinklers for
Water Corporation
Why this oneThe published application rates that convert a station list into a total run time, which is the number that decides whether your design is legal. Pop-up and fixed spray 35 to 45 mm per hour, 13 to 16 minutes per station; rotary 10 to 15 mm per hour, 40 to 60 minutes; gear drive rotary 10 to 20 mm per hour, 30 to 40 minutes; dripline 15 to 20 mm per hour, 30 to 40 minutes; micro spray 35 to 45 mm per hour, 13 to 16 minutes. Target is 10 mm per watering day.
Change this for Perth
The 10 mm per watering day figure is a Perth default for a two-day roster on sandy soil, not a per-plant requirement. Hydrozoning exists precisely so that different stations get different depths and different frequencies — use these rates to convert your chosen depth into minutes, not as a target for every station.
Link checked 2 Aug 2026
Freegovernment10 minPerth / WA
Sprinkler Switch-off
Water Corporation
Why this oneStates the winter ban plainly — 1 June to 31 August every year, across Perth, Mandurah and parts of the South West and Great Southern — and confirms it applies to bore water as well as scheme water, to businesses as well as households. It lists the genuine exemptions, including new lawns and gardens, active sporting surfaces and irrigation fed entirely from a rainwater tank. Read it before you commit to an autumn planting date, because it is the reason a June turf job has to be hand-watered.
Link checked 2 Aug 2026
Freegovernment15 minPerth / WA
Apply for a watering exemption
Water Corporation
Why this oneThe single most useful page for a renovator, and the one most people find out about too late. It covers new gardens and new lawn including roll-on, runners, shredded lawn and seed, for both automatic and manual systems and for bores. It publishes the full graduated establishment schedule — 3.5 mm three times a day for the first ten days in summer, tapering to 10 mm every other day by day 42 — which tells you exactly what run times your establishment program needs and therefore how many stations that program can hold.
Change this for Perth
The exemption is time-limited from the day of planting: up to 42 days between 1 October and 31 March, up to 35 days between 1 April and 30 September. Watering outside the conditions of an exemption risks a $500 fine, so program the controller to revert to the roster on the day it expires rather than trusting yourself to remember.
Link checked 2 Aug 2026
Freegovernment10 minPerth / WA
Garden bore regulation
Department of Water and Environmental Regulation
Why this oneThe state regulator's own statement of the bore rules, and the cleanest wording of the constraint that sets your run-time budget: "You can use a garden bore on two rostered days a week in the Perth and Mandurah area" and "You can use your garden bore once on a rostered day, either before 9am or after 6pm." It also gives the licensing threshold — a licence is needed at 0.2 hectares (2,000 square metres) or more — and confirms the 1 June to 31 August switch-off applies to bores.
Link checked 2 Aug 2026
Freegovernment10 minPerth / WA
Testing your irrigation
Water Corporation
Why this oneYou cannot draw station boundaries on an existing system without running it, and this is the page that tells you how to do that legally. You may run each station "for no longer than two minutes per station", "on your rostered watering days, either before 9am or after 6pm". It also confirms that a Waterwise Garden Irrigator can test on or outside your rostered days and during the Sprinkler Switch-off, which is how a large existing system gets mapped in a single visit in winter.
Link checked 2 Aug 2026
Freearticle20 minPerth / WA
Josh's House landscaping FAQs
Josh Byrne & Associates / Curtin University
Why this oneThe clearest published worked example of hydrozoning on an actual Perth block. It defines the term — "grouping plants based on their common water and management requirements" so that "various hydrozones can be serviced by different irrigation stations, and with different water sources" — then lists the seven hydrozones used at Josh's House in Hilton and the emitter type and water source for each: hardy perennials on greywater sub-surface dripline, turf on bore-fed rotaries, vegetables and fruit trees on dripline, advanced trees on spray stakes on a dedicated station, a propagation area on overhead sprinklers, and natives on dripline for establishment only.
Change this for Perth
The project dates from 2013 and the greywater and bore components are more than a suburban renovation needs. Read it for the hydrozone-to-station logic, which is unchanged, not as a shopping list.
Link checked 2 Aug 2026
Freetool20 minPerth / WA
Waterwise plants
Water Corporation
Why this oneA searchable WA plant directory with a water rating attached to each entry, which is what you need to sort a plant list into hydrozones rather than guessing. It makes the point this lesson depends on — "Think about grouping plants with similar watering needs so you can create a beautiful garden and water more efficiently" — and it is regionally calibrated, defining waterwise differently for northern WA than for Perth and the South West.
Change this for Perth
The water ratings describe established plants. Everything needs more water for its first summer, which is what the establishment program and the watering exemption are for.
Link checked 2 Aug 2026
Freearticle20 minAustralian
DIY irrigation planning guide: pop-up sprinklers with PVC pressure pipe
Holman Industries
Why this onePublishes the per-head flow figures that make the station arithmetic real — roughly 2.3 litres per minute for a 90 degree arc, 4.5 for 180 degrees and 9.1 for 360 degrees — and states the underlying reason for stations at all: "in most cases, it is not possible to run the entire system of sprinklers because you will not have enough water, so we divide the system into zones." Those three numbers let you total a proposed station in about a minute.
Change this for Perth
This is a manufacturer's own DIY guide, so the product recommendations are advertising and the flow figures are for that brand's nozzles at their rated pressure. It covers spray pop-ups on PVC only — no rotors, no dripline — and it does not address mixing emitter types, hydrozones or aspect. Use the published flow of the nozzle you actually specify.
Link checked 2 Aug 2026
FreedirectoryPerth / WA
Find a water specialist
Irrigation Australia / Water Corporation
Why this oneTwo searchable categories matter here: Waterwise Garden Irrigator, for installation, maintenance and repairs, and Waterwise Irrigation Design Shop, for businesses that design systems. If you want a second opinion on a station plan before you trench, the design shops are the filter that separates endorsed designers from general retic sales. The site also states that only a listed Waterwise Garden Irrigator can supply the checklist required for the Water Corporation irrigation rebate.
Change this for Perth
Endorsement means a business has been appointed to deliver the program, not that it is the best designer or the cheapest. Filter by state — the directory lists members outside WA.
Link checked 2 Aug 2026
Paid · $200 application plus $440 pre-qualification exam and $440 general exam for members; $300 / $670 / $670 for non-members; $195 annual renewalcourse6-12 monthsAustralian
Certified Irrigation Designer program
Irrigation Australia
Why this oneThe national industry body's certification, and the formal version of what this mini-course teaches informally. Stage 3, Irrigation System Design Guidelines, covers performance parameters, site considerations, system selection, hydraulic design and monitoring — hydrozoning and station design sit inside it. Worth knowing about so you can recognise the qualification when you engage a designer, and worth doing if irrigation is going to be part of your trade.
Change this for Perth
Explicitly not entry level: it recommends two to three years of irrigation experience or prior formal training such as a Certificate III. For a homeowner designing one garden, the free alternative is the Waterwise Irrigation Design Shop directory above — a design review costs a fraction of the certification and answers your actual question.
Link checked 2 Aug 2026

The rules, with sources

WA regulation changes. Each point below names its primary source and the date it was last checked — always confirm with your own council before you build.

Perth and Mandurah are on a two-day-per-week sprinkler roster, and you may water once on a rostered day, either before 9am or after 6pm. The same roster and times apply to garden bore users as to scheme water users.
Be Groundwater Wise, Department of Water and Environmental Regulation ↗ · checked 2 Aug 2026
$100 on-the-spot fines are issued for breaches of watering rosters. Inspectors operate seven days a week and all complaints are investigated. A controller malfunction does not exempt you from a fine.
Water Corporation ↗ · checked 2 Aug 2026
The Sprinkler Switch-off runs from 1 June until 31 August every year across Perth, Mandurah and parts of the South West and Great Southern. It applies to bore water as well as scheme water, and to businesses as well as households.
Water Corporation ↗ · checked 2 Aug 2026
A watering exemption for a new garden or new lawn lasts up to 42 days from the day of planting between 1 October and 31 March, and up to 35 days between 1 April and 30 September. Not complying with the conditions of an exemption risks a $500 fine, and watering without one is a sprinkler breach.
Water Corporation ↗ · checked 2 Aug 2026
For testing purposes you may run each station for no longer than two minutes, on your rostered watering days, either before 9am or after 6pm. A Waterwise Garden Irrigator may test on or outside your rostered days and during the Sprinkler Switch-off.
Water Corporation ↗ · checked 2 Aug 2026
A garden bore requires a licence if it irrigates 0.2 hectares (2,000 square metres) or more.
Be Groundwater Wise, Department of Water and Environmental Regulation ↗ · checked 2 Aug 2026
Rosters are area-specific and do change. From 1 April 2026 the West Pilbara Water Supply Scheme towns in the City of Karratha moved to three watering days per week for an initial six-month trial, with the same before-9am or after-6pm rule.
Water Corporation ↗ · checked 2 Aug 2026