Questions to ask before sizing an irrigation system
Irrigation sizing depends on area, plants or crops, soil, slope, pressure, water source, storage, filtration, weather, and maintenance. A product list is not a system design.
Map the zones
Separate areas with different plant, soil, shade, slope, wind, or watering needs. Record dimensions, obstacles, drainage, access, and the times the system can run. Include lawns, beds, containers, crops, trees, and areas that should not be watered.
A single zone can be simple, but it may waste water when the areas have different requirements. A zone map gives the installer and future owner something to test when a section is dry or overwatered.
Describe the water requirement
Record what is being grown, its establishment stage, seasonal change, soil, mulch, shade, and the consequence of missed watering. Ask how the design changes for a new planting, mature plants, or a property that must cope with water restrictions.
Do not treat a general litres-per-hour figure as a promise for every garden. The design should explain the assumptions used for demand, scheduling, and weather adjustment.
Measure source, flow, and pressure
Record whether the source is municipal, borehole, tank, rainwater, or mixed. Ask how available flow, pressure, pump capacity, filtration, storage, and pipe run will be measured rather than assumed.
The design should explain what happens when the source is low, electricity fails, filters block, a valve closes, or demand changes. A pump or controller should be selected around the measured system, not only a catalogue maximum.
Plan filtration and water quality
Emitters, valves, pumps, and sprinklers can respond differently to sediment, algae, scaling, or other water-quality conditions. Ask where filtration sits, what the maintenance interval is, and what happens when the filter blocks.
If the source is a borehole, separate the water-use and water-quality decisions from irrigation hardware. A treatment or test recommendation should follow the intended use and a measured result.
Choose emitters around the layout
Compare dripline, point-source emitters, micro-sprays, rotors, sprays, and hand-watering support around the plants, wind, soil, slope, access, and maintenance ability. Ask how the system prevents wetting paths, walls, leaves, or areas that should stay dry.
The method should be understandable to the person operating it. A technically efficient system can still fail if blocked emitters, leaks, or controller settings are difficult to find and repair.
Size zones and schedules
Ask how many zones are required, what each zone delivers, how long it runs, how the controller adjusts for season or rainfall, and how a homeowner can pause or change one area without disrupting the whole property.
Keep the zone map, valve labels, controller settings, seasonal adjustments, and a simple test procedure. The record is part of the system and helps a future technician avoid guessing.
Compare maintenance and ownership cost
Include design, equipment, trenching, installation, delivery, water, electricity, filters, valves, emitters, controller, pump, seasonal changes, replacement parts, labour, and access for repairs.
A system that is inexpensive to install may be difficult to maintain. Ask who responds to a leak, failed controller, blocked filter, low tank, or pump fault and what the call-out costs.
Use planning tools after the system check
An irrigation planning tool can help organise zones and quantities, but it does not measure a property, confirm authority, or certify a pump or installation. Use the output as a conversation document with the installer.
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