Chemical Dosing Pump Calculation
In the field of water treatment, chemical dosing pumps are vital devices used to precisely add chemicals to water for water treatment and purification. Calculations for chemical dosing pumps are a critical step in ensuring that the water treatment process runs effectively and efficiently!
What is a chemical dosing pump?
A chemical dosing pump is a device for automatic chemical dosing, which is mainly composed of a pump body, driving mechanism, control system, and liquid container. By precisely controlling the working speed and time of the pump, a specific amount of chemicals (e.g. chlorinating agent, flocculant, pH adjusting agent, anti-scaling agent, etc.) is accurately dosed into the liquid to be treated to realize the regulation and control of water quality, pH, turbidity, disinfection and sterilization and other parameters.
Why Chemical Dosing Pump Calculation Matters?
An undersized dosing pump may fail to meet treatment targets, while an oversized pump can cause chemical waste, unstable control, and safety risks. Proper calculation ensures:
- Accurate chemical concentration in the process
- Stable operation under variable flow conditions
- Optimized chemical consumption
- Longer pump service life
Calculation of Chemical Dosing Pumps
The formula for chemical dosing pumps usually depends on the type of chemical to be dosed, the water treatment objective and the specific application scenario.
Pharmaceutical Dosage Formula
Dosage (unit: ml/min) = Water Flow (unit: m³/h) × Concentration (unit: mg/L) ÷ 1000
- Water flow rate is the flow rate of the body of water to be treated, usually measured in cubic meters per hour (m³/h).
- Concentration is the concentration of the chemical to be applied in the water, usually measured in milligrams per liter (mg/L).
Key Factors in Chemical Dosing Pump Calculation
Before selecting a chemical dosing pump, it is important to understand several key factors that affect the final dosing flow rate. In many water treatment projects, calculation errors do not come from the pump itself, but from misunderstanding chemical concentration, active ingredient content, density, unit conversion, or dosing mode.
Active Ingredient Concentration
Many chemicals used in water treatment are not 100% pure active ingredients. They are usually supplied as liquid solutions with a certain active concentration.
For example:
| Chemical Solution | Typical Active Ingredient |
| Sodium hypochlorite solution | 10–15% available chlorine |
| Sulfuric acid | 98% H₂SO₄ |
| Sodium hydroxide solution | 30–50% NaOH |
| PAC solution | Depends on product concentration |
| Polymer solution | Usually very low prepared concentration |
When calculating dosing pump capacity, the required dose is usually based on the active ingredient, while the pump actually delivers the chemical solution. Therefore, the active ingredient concentration must be considered.
Formula:
Required Chemical Solution = Required Active Ingredient ÷ Active Ingredient Concentration
Example:
If the required active chlorine dose is 5 mg/L and the sodium hypochlorite solution contains 10% available chlorine:
Chemical solution dose = 5 ÷ 10% = 50 mg/L
This means the dosing pump should be sized based on the actual sodium hypochlorite solution volume, not only the active chlorine demand.
Chemical Density and Specific Gravity
Density is another important factor in chemical dosing pump calculation, especially when converting between mass and volume.
Many dosing formulas start with mass units such as mg/L, g/h, or kg/day, but dosing pumps are usually selected by flow rate, such as L/h, mL/min, or GPH. To convert mass flow into liquid volume flow, chemical density must be used.
Formula:
Volume Flow Rate = Mass Flow Rate ÷ Density
Where:
Density = kg/L or g/mL
Specific Gravity ≈ Density compared with water
For water, the density is approximately:
1 kg/L
But many chemical solutions have higher density. For example, sulfuric acid, sodium hydroxide, and PAC solution may have a density greater than water. If density is ignored, the selected dosing pump capacity may be inaccurate.
Example:
If the required chemical mass is 2 kg/h and the chemical density is 1.2 kg/L:
Dosing flow rate = 2 ÷ 1.2 = 1.67 L/h
So the dosing pump should deliver at least 1.67 L/h before adding a safety margin.
Unit Conversion for Dosing Pump Calculation
In actual projects, chemical dosing data may be provided in different units. Correct unit conversion helps avoid wrong pump selection.
| Unit | Conversion |
| 1 m³ | 1,000 L |
| 1 L | 1,000 mL |
| 1 mg/L | 1 ppm in water-based solutions |
| 1 kg | 1,000 g |
| 1 g | 1,000 mg |
| 1 hour | 60 minutes |
| 1 day | 24 hours |
| 1 GPH | 3.785 L/h |
| 1 L/h | 0.264 GPH |
Common dosing pump flow conversions:
L/h to mL/min = L/h × 1000 ÷ 60
mL/min to L/h = mL/min × 60 ÷ 1000
L/h to GPH = L/h ÷ 3.785
GPH to L/h = GPH × 3.785
Example:
If the calculated dosing flow is 6 L/h:
6 L/h × 1000 ÷ 60 = 100 mL/min
6 L/h ÷ 3.785 = 1.59 GPH
So 6 L/h is equal to about 100 mL/min or 1.59 GPH.
The Importance of Water Treatment Pumps
Accurate dosing of chemicals: The water treatment process usually requires the dosing of chemicals, such as chlorinating agents, coagulants, pH adjusters, etc., to achieve specific water quality treatment goals, to achieve the accuracy and stability of water quality treatment.
Automated operation: Chemical metering pumps are usually equipped with automated control of the dosing system, which can realize the automatic adjustment and control of the dosage of chemicals.
Improve treatment efficiency: Through precise control of the dosage of chemicals, chemical dosing pumps can ensure that each step in the water treatment process can achieve the best results, thereby improving treatment efficiency and reducing waste of resources.
Cost savings: The correct use of chemical metering pumps can avoid overdose of chemicals or chemical waste situation, in addition, chemical metering pumps can also reduce the cost of labor and maintenance costs, and improve the economic efficiency of the water treatment process.
Ensure water quality and safety: The chemical agents added to the water treatment process have a direct impact on the treatment effect and safety of water quality. Chemical metering pumps can ensure the accuracy and stability of the dosage of chemicals to ensure that the treated water quality meets the relevant safety standards and requirements.
The importance of water treatment chemical metering pump in the water treatment process is self-evident, it can ensure the stability, efficiency, and safety of the water quality treatment process, for the normal operation of the water treatment system provides an important guarantee.
Types of Chemical Dosing Pumps
Piston pump: Piston pump is a common type of chemical dosing pump, its working principle is to use the reciprocating motion of the piston in the plunger barrel to realize the suction and discharge of the pharmaceutical. Piston pumps are usually characterized by high pressure, high precision and stability, and are suitable for occasions with strict requirements on the dosage of chemicals. The HJ-Z Mechanical Dosing Pump is an excellent choice.
Dosing pump: Dosing pumps realize the suction and discharge of chemicals through the up and down movement of diaphragm, so as to realize the dosage of chemicals. Solenoid dosing pumps usually have good sealing and corrosion resistance, and are suitable for the dosing of various chemicals.
Peristaltic pump: Peristaltic pump through the rotary movement of the roller or squeeze plate, the liquid in the hose will be pushed forward, to achieve the delivery of pharmaceuticals and dosing. Peristaltic pump has simple, compact, easy-to-maintain the characteristics of some of the need for low-flow, high-precision occasions.
Gear pump: Gear pumps use the rotary motion of the gear to inhale and discharge the agent to achieve the pharmaceutical dosage. Gear pumps have the characteristics of stable flow rate and smooth pressure, which are suitable for some occasions with high flow rate requirements.
Each type of chemical metering pump has its applicable occasions and advantages and disadvantages, Choosing the right type should be based on specific application needs and process requirements for comprehensive consideration.
Safety Factor and Pump Selection Recommendations
In real engineering applications, the calculated value should not be used directly as the pump’s maximum capacity.
Best practices:
- Select pump rated flow ≥ 1.2 × calculated flow
- Keep normal operation within 30–80% of pump capacity
- Check pressure capability, material compatibility, viscosity, and suction conditions
This approach improves control accuracy and reduces mechanical stress.
Typical Chemical Dosing Pump Applications
| Application | Typical Dosage Range |
| Chlorination (NaOCl) | 1–10 mg/L |
| pH control (acid/alkali) | Process-dependent |
| Coagulant (PAC) | 10–200 mg/L |
| Polymer (PAM) | 0.5–5 mg/L |
| RO antiscalant | 2–6 mg/L |
Each application may require additional corrections based on reaction efficiency, temperature, and water quality.
Pump Calibration And Maintenance
Calibration
- Regularly calibrate the flow rate and pressure of the pump to ensure the accuracy of its dosage. The frequency of calibration can be determined according to the use of the situation and the manufacturer’s recommendations, usually every certain period or in the event of abnormalities in the calibration.
- Use calibration column for calibration, and follow the calibration methods and procedures provided by the manufacturer.
- During the calibration process, pay attention to checking and adjusting the working parameters of the pump, such as flow rate, pressure, speed, etc., to ensure that it meets the predetermined standards and requirements.
Maintenance
- Regularly clean the inside and outside of the pump to remove the dirt and foreign matter accumulated inside the pump to ensure the smooth operation of the pump.
- Check and replace the seals, valves, pipes and other wearing parts of the pump to ensure its normal operation and sealing performance.
- Regularly lubricate the bearings and moving parts of the pump to ensure its smooth operation and long life.
- Check and adjust the installation position and connection of the pump to ensure that it is solid and reliable, and reduce vibration and noise.
- Pay attention to the running status of the pump, find and deal with abnormal conditions in time, such as abnormal noise, water leakage, temperature abnormality, etc., in order to prevent pump failure and damage.
Common Mistakes in Chemical Dosing Pump Calculation
- Confusing solution dosage with active ingredient dosage
- Ignoring chemical density differences
- Selecting pumps with no flow adjustment margin
- Overlooking back pressure and suction conditions
- Using theoretical values without safety factors
Avoiding these errors significantly improves system reliability.
Summary
Proper chemical dosing pump calculations not only improve the treatment efficiency of water treatment systems and reduce wasted resources, but also reduce operating costs and protect the environment and public health.
The Haosh pump manufacturer has advanced production facilities and a technical team that is constantly working on technological innovations and optimization of dosing metering pumps to ensure that the performance and quality of its products are always at the forefront, as well as providing pump equipment such as agitators, accessories and pulsation dampeners.