Smart irrigation controllers and rain sensors: how to choose and set them up

The controller is the brain of an irrigation system. It decides which zones run, on which days, at what time and for how long. Most watering waste comes from a controller set once and never changed: running in winter the same as in summer, watering the day after a storm, or giving a shady side lawn the same time as a sunny back lawn.

Smart controllers and rain sensors can fix much of that automatically. But they’re only as good as the information you give them. Sydney Water puts it bluntly: automatic systems that aren’t well designed, programmed and maintained can use more water than a garden needs.

This guide covers the types of controller, what “smart” really means, how to set one up properly, and how to keep it working.

The options

Tap timers

Battery-powered timers that screw onto a garden tap and turn it on and off on a schedule. They’re cheap and simple, and suit a single hose-end sprinkler or a small drip line. Most can’t adjust for weather, and you need one per tap.

Standard controllers

A wall-mounted controller that operates solenoid valves, one for each zone. You set the days, start times and run time for each zone. Many have a seasonal adjustment that scales every zone up or down by a percentage, and a rain delay button that pauses watering for a set number of days. They don’t change anything unless you do.

Smart controllers

A smart controller adjusts its own schedule. Power and Water’s Living Water Smart program describes it simply: an irrigation controller that automatically adjusts watering based on local weather conditions. When it rains, it reduces or turns off watering; when it’s hot, it can increase it.

They get their information in different ways:

• Weather-based controllers use Wi-Fi to download local weather data. Sydney Water notes that some use free local data from the Bureau of Meteorology. In Darwin, Living Water Smart’s Weather Web network of local weather stations can feed data to compatible controllers.
• Sensor-based controllers use sensors at your house, such as a rain sensor or soil moisture sensor.

Most smart controllers also have an app, so you can check or change the schedule from your phone.

Rain sensors

A small device mounted outside that detects rain and stops the controller from watering until it dries out. Many standard controllers have a terminal for one. They’re one of the cheapest water-saving upgrades for an existing system.

Soil moisture sensors

A sensor buried in the root zone that tells the controller how wet the soil is. Sydney Water describes these as an optional extra that gives the controller more feedback. Placement matters: a sensor in a shady, damp spot will under-water a sunny lawn.

Flow meters

A flow meter measures how much water each zone uses. Paired with a smart controller, it can alert you to a broken head or burst pipe, which otherwise can run unnoticed for weeks.

Will it save water?

It depends on how you water now. Living Water Smart says a smart controller could save from 20% to 50% on water costs, and that most of the 650 Darwin households it consulted were overwatering. If you already adjust your schedule through the year and switch off after rain, the savings will be smaller. If your controller hasn’t been touched since it was installed, they may be large.

Any controller, smart or not, saves water only if the rest of the system works. Fix broken heads, blocked nozzles and uneven coverage first. A smart controller can’t fix a sprinkler that waters the driveway.

Upgrading from tap timers

Moving from tap timers to a central or smart controller is more than swapping one box for another. Living Water Smart notes that it’s likely to need an irrigation specialist to install:

• an isolation valve, so the whole system can be turned off;
• a backflow prevention device, to protect the drinking water supply;
• solenoid valves for each watering zone;
• a strong, consistent Wi-Fi signal where the controller will be;
• an outdoor power point.

Work on the connection to the mains water supply may need a licensed plumber. Check your water authority’s requirements before you start.

Setting it up properly

A controller is only as good as its program. Take an hour to set it up from measurements, not guesses.

1. Map your zones

Run each valve in turn and note what it waters: the back lawn, the side strip, the garden beds. Give each zone a clear name in the controller or app.

2. Describe each zone

Smart controllers usually ask about each zone. Have the answers ready:

• plant type: lawn, garden bed, trees;
• sprinkler type: pop-up sprays, rotary nozzles, rotors, drip;
• soil: sandy, loam or clay;
• sun: full sun, part shade or shade;
• slope: flat or sloping;
• application rate: how many millimetres an hour the zone applies.

3. Measure the application rate

Do a catch-cup test on each zone. It tells you how many millimetres each zone applies in a set time, which the controller needs to work out run times. The Sprinkler Run-Time Calculator turns your readings into minutes for your watering target.

4. Program the rules

Enter your water authority’s allowed watering days and hours. Rules differ widely:

• Perth has a rostered sprinkler system by address and a winter sprinkler switch-off.
• Icon Water’s permanent measures in Canberra set the hours when sprinklers can run in the warmer months.
• Sydney Water’s Water Wise Guidelines set rules for sprinklers and watering systems.

A smart controller won’t know your local rules unless you enter them. Update them when restrictions change.

5. Use cycle and soak

On clay soil and slopes, set each lawn zone to run in two or three short cycles with a break between them. Water soaks in instead of running off. Most smart controllers have a cycle-and-soak setting.

6. Set weather triggers

Many smart controllers let you set rules for how they respond to the weather. Living Water Smart’s recommended triggers for Darwin include:

• turning irrigation off when it rains over 10 mm;
• decreasing irrigation by 50% when it rains over 5 mm;
• turning irrigation off when the last seven days’ rainfall is over 30 mm;
• increasing irrigation by 20% if the forecast temperature is over 35 degrees;
• delaying irrigation if wind over 50 km/h is forecast.

These are set for Darwin’s tropical climate. Use them as a guide to the kinds of rules you can set, and adjust the numbers for your climate and lawn.

Installing a rain sensor

Follow the manufacturer’s instructions. In general:

• mount it where rain falls on it freely, not under eaves or trees;
• keep it out of reach of the sprinklers, or it will switch the system off every time it runs;
• connect it to the sensor terminals on the controller, and turn the sensor setting on;
• test it by wetting the sensor and checking the controller pauses.

Through the year

Even a smart controller needs a check each season.

In the tropics, follow the wet and dry seasons instead. Living Water Smart notes that paying attention to the weather is especially useful during the wet season and the periods either side of it, when rain can be patchy.

Troubleshooting

Choosing a controller

• Enough zones for your system now, and one or two spare.
• Weather data for your area, or sensor support if you prefer measuring at home.
• Per-zone settings for soil, sun, slope and sprinkler type.
• Cycle and soak, seasonal adjustment and rain delay.
• Watering-day restrictions you can program to match your local rules.
• Manual control at the unit as well as in the app.
• A water-efficiency certification. Smart Approved WaterMark is an Australian certification for water-efficient products.

Common mistakes

• Setting it and forgetting it, smart or not.
• Guessing zone details instead of doing a catch-cup test.
• Not programming local water rules.
• Mounting the rain sensor under the eaves or in sprinkler spray.
• Using the same run time for every zone.
• Expecting the controller to fix broken heads or poor coverage.

Log it

Log changes to your controller settings in your Lawn Journal, with the date and why you made them. Alongside your watering log and rainfall, it shows whether the schedule is working and makes next season’s adjustments quicker.