How to Select a Metering Pump: Flow, Pressure and Materials
Many buyers focus only on price and end up with a pump that cannot deliver enough flow, withstand the pressure, or resist the chemical. Here is how to get it right.
1. Determine the Flow Rate
Size the pump at 1.2–1.5× your maximum dosing requirement to leave adjustment headroom. For example, if the process needs 10 L/h, choose a model rated around 15 L/h. Running at 50–80% stroke gives the best accuracy.
2. Determine the Pressure
The pump's rated pressure must exceed the system backpressure (pipe friction + static head + valve differential), generally by at least 20%. Otherwise the chemical simply will not be injected.
3. Wetted Materials
| Chemical | Recommended material | |----------|---------------------| | Sodium hypochlorite, dilute acids | PVC / PTFE | | Concentrated sulfuric acid, strong alkali | PTFE / PVDF | | Flocculants (PAC/PAM) | PVC / stainless steel |
4. Solenoid or Mechanical?
- Solenoid diaphragm pumps: low flow (< 30 L/h typically), low pressure, economical — great for pools and small dosing tasks.
- Mechanical diaphragm pumps: high flow and pressure, built for continuous industrial duty.
5. Other Considerations
- Analog (4-20mA) or pulse control requirements
- Closed-loop dosing with online water quality analyzers
- Power supply and ingress protection (IP65+ outdoors)
Unsure about your process parameters? Contact us for free selection advice.