Choosing the correct dosing pump size is one of the most important decisions when setting up a fertigation, livestock medication, or water treatment system. Selecting the wrong size can lead to inaccurate dosing, poor system performance, or unnecessary cost.
In this guide, we’ll break down exactly how to choose the right dosing pump for your application, including flow rate, dosing ratio, and real-world examples.
What Is a Dosing Pump?
A dosing pump (also known as a proportional injector) is designed to automatically inject a precise amount of chemical, fertiliser, or additive into a water line based on flow rate.
Unlike electric dosing systems, water-powered units such as Dosatron pumps operate without electricity and adjust dosing automatically as flow changes.
The 3 Key Factors That Determine Pump Size
1. Water Flow Rate (L/Min)
This is the most important factor.
You need to know:
- How much water is flowing through your system (litres per minute)
- Peak flow, not average flow
Example:
- Small garden irrigation → 10–20 L/min
- Greenhouse or fertigation system → 20–80 L/min
- Large farms or washdown → 80–300+ L/min
👉 Your dosing pump must fall within this flow range.
2. Dosing Ratio (%)
This determines how much chemical is injected.
Typical ranges:
- 0.2% – 2% → fertilisers, nutrients
- 1% – 5% → general applications
- Higher ratios → cleaning chemicals or specific treatments
Example:
- 1% dosing = 1 litre chemical per 100 litres water
👉 Always match the pump’s ratio range to your application.
3. Application Type
Different applications require different pump characteristics.
Fertigation
Livestock Medication
- Accurate dosing is critical
- Medium flow ranges
- Chemical compatibility matters
Washdown & Cleaning
- Higher dosing ratios
- Higher flow capacity
Water Treatment
- Depends on chemical type and flow rate
- Often continuous dosing
How to Choose the Right Size (Step-by-Step)
Step 1: Identify your maximum flow rate
Check:
- pump specs
- pipe size
- irrigation design
Step 2: Choose your dosing percentage
Based on:
- chemical manufacturer recommendations
- application type
Step 3: Match to a dosing pump range
Example:
| Flow Rate | Recommended Pump Type |
|---|---|
| 5–40 L/min | Small range (D8, D07) |
| 20–100 L/min | Medium range (D20, D25) |
| 100–500 L/min | Large range (D30, D45, D90) |
Real-World Examples
Example 1: Small Farm Irrigation
- Flow: 25 L/min
- Application: Fertigation
- Solution: Mid-range dosing pump (e.g. D25)
Example 2: Livestock Water Medication
Example 3: Washdown System
- Flow: 120 L/min
- Requirement: Higher dosing percentage
- Solution: Larger unit (D30+)
Common Mistakes to Avoid
❌ Choosing based on price only
Undersized pumps won’t perform properly.
❌ Ignoring peak flow
Always size for maximum demand.
❌ Wrong dosing ratio range
Leads to incorrect chemical injection.
❌ Not considering future expansion
Always allow room to scale.
Dosatron vs Venturi Sizing (Quick Tip)
Venturi injectors rely on pressure differential and are less precise.
If your application requires:
- consistent dosing
- variable flow
- accuracy
👉 A Dosatron-style proportional pump is the better choice.
Need Help Choosing the Right Pump?
Choosing the right dosing pump can be confusing — especially when balancing flow rate, ratio, and application.
👉 View our full range of dosing pumps
👉 Or contact our team for expert advice tailored to your system
FAQs
What happens if my dosing pump is too small?
It will restrict flow and may not dose correctly, especially at higher demand.
Can I oversize a dosing pump?
Yes, but it must still operate within its minimum flow range.
Do dosing pumps require electricity?
Water-powered dosing pumps like Dosatron operate without electricity.
How accurate are dosing pumps?
High-quality proportional injectors provide very accurate dosing across varying flow rates