By Dave Miller · off-grid sparky · 22 years wiring solar, batteries and sheds in central QLD

“After frying a $400 pump in my first central QLD summer, I learned never to size solar arrays without accounting for a 30% derating factor.”

Stop wasting cash on pumps that don’t work. Solar irrigation for off-grid Aussie living isn’t rocket science. Here’s how to do it right, without the sales pitch.

Pump Sizing: Don’t Be a Dumb Aussie

Under-sizing = dead garden. Over-sizing = wasted money. Calculate properly:

• Flow rate (L/hr): Multiply your garden area (m²) by 5. Example: 50m² garden = 250L/hr minimum.
• Head (m): Vertical lift + pipe friction. Measure from pump to highest point + 10% for pipe loss. 10m lift? Use 11m in calculation.
• Rule of thumb: Get a pump rated 20% higher than your calculated flow/head. Dust, heat, and clogged filters kill pumps.

Pipe Design: Stop Wasting Water (and Cash)

Wrong pipe size = no water at the end of the line. Here’s the fix:

• Size matters: Use 16mm or 20mm PVC for most off-grid setups. Bigger = more cost, more friction. 16mm is fine for 100m runs max.
• Minimise bends: Every 90° bend = 30% flow loss. Use 45° elbows where possible. Straight lines only.
• Pressure check: If your taps dribble, you’ve got too much pipe or too many bends. Cut back.

Automation: Set It and Forget It (But Actually Check It)

Manual watering is for people who enjoy sweating. Automation saves time and water. Do this:

• Timer only: $50-80 at Bunnings. Set to run 30 mins at dawn. Simple. Works. No apps needed.
• Soil sensor (worth it): $40-60 (Jaycar). Stops pumping when soil’s wet. Saves 30% water. Don’t skip this.
• NO smart home nonsense: Avoid Bluetooth/WiFi pumps. They die in the outback. Stick to basic timers.

Real Aussie Pricing (indicative prices)

• Solar pump (1000L/hr): SunPump 1.5kW - $1,450 (via Solar Wholesale). No cheaper option works reliably.
• Pipe (50m): 16mm PVC - $90 (Bunnings). Don’t buy 25mm. You’ll regret it.
• Automation: Basic timer + soil sensor - $95 (Jaycar). Skip the $200 "smart" kit.

Final Word

Don’t overcomplicate it. Size the pump right, pipe it straight, automate simply. Your garden won’t care about fancy tech. It just wants water. Get it done. Stop reading. Go buy the pump.

When to Call a Professional

While many off-grid projects are achievable as DIY, certain situations require licensed professionals:

• Electrical work beyond basic 12V DC additions — requires a licensed electrician
• Structural modifications to buildings or load-bearing elements
• Gas line installation or modification
• Solar array installations above safe voltage thresholds
• Any work that affects the structural integrity of your property

Always check local regulations and obtain necessary permits before commencing work.