How to plan a watering system that actually works: test your water, split the garden into zones, size the pipe, choose the right sprinklers or drip, and match each to the plants it suits.
Open the blueprint planner Use its irrigation layer to draw your design and check each zone.
Two numbers decide what you can run: static pressure (how hard the water pushes when nothing is running) and flow (how much water the tap can deliver). The planner asks for both.
Typical mains pressure is about 200 to 500 kPa (30 to 70 psi). Below about 200 kPa you will struggle to run rotors or long pipe runs. Above about 500 kPa (70 psi) fit a pressure-reducing valve to protect fittings. Check the pressure rating printed on your pipe and fittings.
An irrigation zone is a group of heads or drip lines opened by one valve and watered at the same time. You need several zones because a typical tap cannot feed the whole garden at once.
Add up the flow of everything in a zone (each head's flow, or drip line length × flow per metre). Keep it to about 75% of your measured tap flow. The margin covers pressure losses in pipe and fittings and the fact that the flow you measured is at an open tap with no pressure left.
Worked example: tap flow 20 L/min, so the zone limit is 15 L/min. Small rotors that use 5 L/min each give 3 heads per zone. A 40 m drip line using 6.7 L/h per metre uses 268 L/h, or 4.5 L/min, so it is a small load and can share a valve only with similar drip.
Water loses pressure as it moves through pipe (friction). Longer pipe, higher flow and smaller pipe all increase the loss. If too much is lost, the last heads get weak pressure and spray short.
Required pressure at the valve ≈ head operating pressure + friction loss in the pipe + about 20 kPa (3 psi) for the valve and fittings. Compare it with the pressure available at the flow you will use, which is always lower than the static pressure.
Keep water speed under about 1.5 m/s (5 ft/s) to avoid noise and water hammer. That limits the flow each pipe size should carry:
| Poly pipe size | Approx. maximum flow |
|---|
Calculated with the Hazen-Williams formula (C = 140 for poly pipe). Real pipe varies with the make, fittings and bends, so allow a margin. The planner adds 15% for fittings.
| Type | Throw | Flow per head | Pressure | Water applied | Best for | Watch out for |
|---|---|---|---|---|---|---|
| Pop-up spray | 2 to 5 m (6 to 15 ft) | 3 to 10 L/min (1 to 3 gal/min) | 170 to 280 kPa (25 to 40 psi) | 35 to 50 mm/h | Small lawns, dense groundcover, odd shapes | Runoff on clay and slopes; wind drift; misting at high pressure |
| Rotor (gear-drive) | 5 to 15 m (17 to 50 ft) | 4 to 40 L/min (1 to 10 gal/min) | 280 to 400 kPa (40 to 60 psi) | 8 to 15 mm/h | Medium and large lawns, open areas | Needs good pressure; too coarse for small or narrow areas |
| Rotary nozzle (MP type) | 2 to 9 m (6 to 30 ft) | 0.5 to 4 L/min (0.1 to 1 gal/min) | 200 to 400 kPa (30 to 60 psi) | 8 to 12 mm/h | Lawns on clay or slopes, wind, replacing sprays | Cannot be mixed with spray nozzles on the same zone |
| Impact sprinkler | 8 to 20 m (26 to 65 ft) | 15 to 60 L/min (4 to 16 gal/min) | 250 to 400 kPa (35 to 60 psi) | 10 to 20 mm/h | Paddocks, rough ground, large open areas | Noisy; needs high flow; throws far |
| Micro-sprinkler (stake) | 1 to 3 m (3 to 10 ft) | 0.3 to 1.7 L/min (20 to 100 L/h) | 100 to 200 kPa (15 to 30 psi) | 10 to 30 mm/h | Shrub beds, orchards, tree roots, nurseries | Blocked by foliage; evaporates in wind |
| Bubbler | Floods a small basin | 2 to 8 L/min (0.5 to 2 gal/min) | 100 to 200 kPa | Floods the root zone | Single trees, planting basins | Runoff on slopes; needs a basin |
Drip delivers water slowly right at the roots, which saves a lot of water, reduces weeds and keeps foliage dry. It also needs much less pressure and flow than sprinklers, so you can run bigger zones.
| Type | Typical output | Best for | Notes |
|---|---|---|---|
| Dripline (inline emitters) | 1 to 2.3 L/h per emitter, every 20 to 50 cm | Garden beds, hedges, vegetable rows, groundcover under mulch | The all-rounder. Choose pressure-compensating line on slopes and long runs. Typical maximum run is about 50 to 100 m for 16 mm line, so check the chart. |
| Point emitters (on 4 mm tube or 13 mm pipe) | 2 to 8 L/h each | Trees, large shrubs, pots, scattered plants | Use 2 to 4 emitters around a tree and move them out as the tree grows. |
| Drip tape | 1 to 2 L/h, thin wall | Annual vegetable beds | Cheap, low pressure (about 50 to 100 kPa), but lasts a season or two. Not for mulched perennial beds. |
| Sub-surface drip | As dripline | Lawn and long-term beds | No evaporation and no surface mess. Use root-intrusion-protected emitters and flush regularly. |
| Soaker hose | Uneven | Small vegetable beds and temporary use | Keep runs under about 15 m (50 ft) because output drops sharply along the hose. |
| Micro-sprays and jets | 20 to 100 L/h | Groundcover, orchards, open beds | Waters a small circle rather than a point. |
| Plants or place | Best system | Why and how |
|---|---|---|
| Lawn, large areas | Rotors or rotary nozzles | Even coverage, slow enough to soak in. Water deeply 1 to 3 times a week rather than a little every day. |
| Lawn, small or odd-shaped | Pop-up sprays or rotary nozzles | Fit awkward corners. Keep spray and rotor types on separate zones. |
| Vegetable beds and raised beds | Dripline or drip tape, 20 to 30 cm spacing | Steady moisture at the roots, dry leaves (fewer diseases like blight and mildew), less weeding. |
| Fruit and shade trees | 2 to 4 point emitters, bubbler or micro-sprinklers | Deep, infrequent watering encourages deep roots. Place emitters near the drip line (edge of the canopy), not at the trunk. |
| Orchards and citrus | Micro-sprinklers or dripline loops | Wet a larger root area as the trees mature. |
| Mixed shrub and perennial beds | Dripline under mulch | Efficient and hidden. Group by water need. |
| Hedges and screens | Dripline along one or both sides | Even water along the row. |
| Groundcover | Rotary nozzles, micro-sprays or dripline | Wide spread that drip alone may not cover until the plants join up. |
| Native and drought-tolerant gardens (banksias, grevilleas, proteas, many Mediterranean plants) | Drip, set to run rarely | Water deeply and occasionally while they establish (the first one or two summers), then taper off. Many of these plants dislike wet feet and some are sensitive to summer irrigation, so avoid overhead spray and frequent wetting. |
| Succulents, cacti, rock gardens | Minimal drip | Very little water, with free-draining soil. |
| Pots, planters, hanging baskets | Point emitters or spaghetti tube with a timer | Pots dry out fastest, so they usually need their own zone on a short, frequent schedule. |
| Slopes | Pressure-compensating drip or rotary nozzles | Cycle and soak (short runs repeated) so water soaks in rather than running off. Fit check valves at the low end. |
| Sandy soil | Any, with shorter and more frequent runs | Water drains straight through, so apply smaller amounts more often. |
| Clay soil | Drip or slow-rate heads, longer gaps | Water soaks in slowly, so use low flow rates and long intervals. |
The planner's plant results show each plant's water need (low, medium or high). Put plants of the same need on the same zone.
A starting point for the supplemental water a garden needs in peak summer when there is little rain. Adjust for your climate, soil and the weather.
| Plants | Depth per week | Notes |
|---|---|---|
| Lawn, vegetables, roses, thirsty plants | About 25 mm (1 in) | Split into 2 to 3 runs. Use 4 runs on sand. |
| Medium-water shrubs and perennials | About 15 mm (0.6 in) | 1 to 2 runs a week. |
| Established low-water and native plants | About 5 to 10 mm (0.2 to 0.4 in), or none | Water deeply and rarely, and only in hot dry spells once established. |
Run time = weekly depth ÷ application rate × 60. For example, 25 mm a week with rotors applying 10 mm/h is 150 minutes a week, or three runs of 50 minutes. Hotter climates need about 25% more, cooler ones about 30% less. New plantings need more water, more often, for their first one or two summers.
For drip, the planner assumes dripline rows about 0.5 m apart (about 13 mm/h). Point emitters have no fixed area, so go by feel: soak the root zone, check the soil 10 to 20 cm down, and adjust.
In the blueprint planner, open the Irrigation layer panel, enter your static pressure and tap flow, then place a tap, valves, heads, drip lines and pipes. Give each part a zone number. For every zone it:
It is a planning aid, not a design guarantee. Head flows and pressures come from typical values, so check the manufacturer's chart for the products you buy, and have a licensed plumber handle connections to mains water.
Quick conversions: 1 psi = 6.895 kPa, 1 gal/min = 3.785 L/min, 1 in = 25.4 mm, 1 ft = 0.3048 m.