How to check an installer sizes and designs the system properly

Most homeowners discover their new irrigation system is undersized or poorly designed only after months of struggling with dead patches, waterlogged clay, or zones that won't reach the back fence. By then, the installer has moved on, and fixing it costs nearly as much as the original job. The root cause is almost always one of these oversights: the designer never measured the garden properly, guessed at soil type, ignored microclimates, or scaled the pump and valve sizes down to save money upfront.

The difference between a system that thrives and one that fails starts long before trenches are dug. It lives in the site survey—the methodical walk-through where a competent installer maps your garden, notes slopes, identifies compacted vs. open areas, and asks about your water source. Skip this, and everything downstream is compromise.

The survey that should take hours, not minutes

A proper site visit is not a quick walk around. The installer should mark out bed boundaries, measure distances from the water source to the furthest outlet, photograph problem areas (dry corners, boggy patches, slopes), and ask detailed questions about soil. If someone sketches your garden from a few snapshots or a drone photo alone, walk away. They are working blind. Ask them to visit during different times of day if possible—morning and afternoon light reveal microclimates and shade patterns that affect plant survival. The survey notes should go into the quote; if they don't, there is nothing to fall back on if the system underperforms.

Sizing that matches your water source and soil

The pump and valve sizes must suit both your water supply and the area you are covering. A common mistake is oversizing the pump to "be safe"—this wastes energy and money, strains your mains connection, or depletes a borehole faster than sustainable. Equally, undersizing creates pressure drops: outer zones won't wet properly while inner zones flood. The installer should calculate flow rates in litres per minute for each zone and cross-reference them against your water source (municipal pressure, borehole yield, tank capacity). If they don't mention this calculation in the quote, they are guessing.

Soil type changes everything. Clay drains slowly; sandy soil drinks fast and dries out. A decent installer will do a simple permeability test—digging a hole, filling it, and timing how fast water drains—or at least ask probing questions about how water behaves in your garden after rain. Different zones often need different sprinkler types and spacing. A shaded mulched bed needs far less water and frequency than an open sunny lawn.

Zoning that splits plants by their thirst

A system dumping equal water on all plants is a system that works for nobody. Lawns, shrub beds, and vegetable gardens have different water needs and different root depths. A sprinkler layout should separate these into distinct zones, each on its own valve with its own run time. The installer should walk you through why each zone is configured as it is. If the design just draws circles on a plan without explaining coverage gaps or overlap, ask them to justify it. Overwatering is the fastest way to kill plants and waste water—and it starts with poor zoning logic.

Drawings and sign-off before work begins

Before a single stake goes in the ground, you should have a labelled site plan showing sprinkler positions, valve locations, pipe routes, zone boundaries, and run times. This is your baseline. Once the system is installed, walk it with the installer during a test run. Turn on each zone separately and watch where water lands. Dry patches or over-spray now are problems to fix before final sign-off, not months later when establishment is critical.

When comparing installers, don't just ask for a price. Ask to see their survey notes, ask how they calculated zone sizes, ask why zones are arranged that way. The installer who can explain this reasoning clearly is the one who measured carefully. That discipline is what separates systems that grow your garden from systems that waste your water and frustrate you for years.