Pump Sizing Guide
Choosing the right pump size is about matching flow and head to the job, then checking that the pump can cope with your worst‑case conditions.
Pump sizing basics for irrigation
For irrigation, start by calculating how much water you need per day and over what run time you want to deliver it.
Daily demand: total megalitres per day for your paddocks, pivots or sprinklers.
Operating hours: how many hours per day you plan to run the pump.
Required flow: convert ML/day to litres per second (L/s) to match pump curves and specifications.
You then add total head (static lift + pipeline friction + elevation) to find the duty point, and select a pump that delivers that flow at that head with a sensible margin.
Emergency dewatering and flood response
Emergency dewatering is all about high flow in short windows, often with dirty water, debris and variable suction levels.
Diesel-driven, self‑priming pumps are ideal for emergency use because they start quickly, cope with fluctuating suction and do not rely on mains power.
When sizing for dewatering or flood control, focus on peak inflow (worst‑case rainfall or seepage) and target a pump or combination of pumps that can comfortably exceed that inflow rate.
Industry-specific considerations
Farming and irrigation: focus on seasonal water demand, field layouts and availability of power vs diesel.
Construction: factor in site constraints, solids handling, run time and the need for mobile trailer or skid‑mounted packages.
Mining: allow for abrasive water, long duty cycles and redundancy; multiple large pumps may be required for pit or sump dewatering.
Pump size and flow rate chart
The table below shows typical flow ranges for Collins Pumps’ 6, 8, 10 and 12‑inch diesel pump sizes, in both megalitres per day and litres per second.
Pump size (inch) Flow range (ML/day) Approx. flow range (L/s)
6 inch 2 – 7 ML/day 23 – 81 L/s
8 inch 4 – 9 ML/day 46 – 104 L/s
10 inch 5 – 12 ML/day 58 – 139 L/s
12 inch 12 – 18 ML/day 139 – 208 L/s
(Conversions based on 1 megalitre = 1,000,000 litres and 86,400 seconds per day.)
Use this chart as a starting point: estimate your required ML/day, convert to L/s, then look at which pump size spans that flow at the heads you’re working with. If you share a sample job (e.g. 6 ML/day from a river to a 2 km main with 20 m lift), I can step through which size is most appropriate.