The performance of a dosing pump depends heavily on how the suction and discharge piping is designed. Even a correctly sized and installed pump will deliver inconsistent dosing, air-locking, and pressure fluctuations if the piping layout is incorrect. Proper piping design ensures accurate chemical injection, stable flow, easy maintenance, and long-term system reliability.
This guide explains best practices for suction and discharge piping design in dosing systems used in RO plants, cooling towers, swimming pools, wastewater treatment, boilers, and chemical dosing skids.

​1. Importance of Proper Piping Design
Why It Matters

• Ensures stable and accurate dosing
• Prevents air-locking and cavitation
• Improves priming capability
• Reduces pressure spikes
• Prevents backflow and siphoning
• Enhances pump lifespan

Both suction and discharge sides must be designed according to the pump manufacturer’s requirements.

2. Suction Piping Design
The suction line is the most sensitive part of the dosing system. Any mistake here directly affects dosing accuracy.

2.1 Keep the Suction Line Short and Straight
Best Practice

• Place the dosing pump close to the chemical tank
• Minimize bends, elbows, and vertical lifts

Why
Long suction lines increase friction losses and the chance of air entry.

2.2 Use the Correct Suction Tubing Material
Selection Based On

• Chemical compatibility
• Temperature
• Suction lift or flooded suction

Common materials include PVC, PTFE, PVDF, and reinforced chemical hoses.

2.3 Prefer Flooded Suction Arrangement
Benefits

• Zero suction lift improves priming
• Reduced air-locking
• Better accuracy at low dosing rates

This is highly recommended for antiscalant, coagulant, and chlorine dosing.

2.4 Install a Foot Valve with Strainer
Purpose

• Prevents backflow
• Keeps the suction line primed
• Stops debris from entering the pump

Placement

• 5–10 cm above bottom of chemical tank
• Away from sediment, sludge, or crystallized deposits

2.5 Ensure All Connections Are Airtight
Even small air leaks cause:

• Air-locking
• Inaccurate dosing
• Failure to prime

Use PTFE tape, proper ferrules, and chemical-resistant fittings.

2.6 Vertical Rise and Suction Lift Limitations
General Guidelines

• Maximum 1.5 m suction lift for most diaphragm dosing pumps
• Avoid unnecessary elevation differences

Dosing pumps are not designed to handle high suction lifts.

3. Discharge Piping Design
The discharge line must ensure stable, pulsation-free chemical delivery into the process pipeline.

3.1 Use Proper Pressure-Rated Tubing
Discharge lines must handle system pressure plus pump pressure.
Recommended Materials

• PTFE
• PVDF
• PE or HDPE
• SS316 for industrial high pressure

Avoid low-pressure vinyl or rubber hoses.

3.2 Install a Back-Pressure Valve
Why It’s Critical

• Prevents uncontrolled flow
• Ensures accurate dosing
• Provides minimum required discharge pressure

Back-pressure valves are essential in low-pressure systems such as cooling towers and swimming pools.

3.3 Add a Pressure Relief Valve
This protects the pump head from overpressure when:

• Downstream line is blocked
• Valve is closed
• Injection point is clogged

Relief valve should discharge safely back into the chemical tank.

3.4 Install a Pulsation Dampener if Needed
Benefits

• Reduces pressure spikes
• Smoothens pulsating flow
• Protects instruments like flowmeters and pressure gauges

Recommended for high-pressure or long discharge lines.

3.5 Minimize Bends and Use Smooth Routing
Sharp bends increase backpressure and pulsation.
Best Practice

• Keep the discharge line as straight as possible
• Use sweep elbows instead of sharp 90-degree fittings

3.6 Avoid Excessive Vertical Height Differences
Injecting chemical into a high elevation point increases pressure demand.
Solution
Ensure pump pressure rating exceeds maximum discharge height + pipeline pressure.

4. Proper Installation of the Injection Point
4.1 Use an Injection Quill
An injection quill ensures:

• Correct chemical mixing
• Injection into the center of the pipeline
• Prevention of pipe wall corrosion

4.2 Confirm Flow Direction
Wrong installation reduces effectiveness and may damage the quill.
4.3 Check Quill Length
It should reach one-third into the pipe diameter.

5. Preventing Backflow and Siphoning
Backflow can occur if pump stops while system pressure changes.
Preventive Components

• Non-return valve
• Anti-siphon valve
• Properly placed back-pressure valve

This is especially important when chemical tank is positioned above injection point.

6. Supporting and Securing Piping
Best Practices

• Use pipe clamps to prevent vibration
• Keep pipes away from hot surfaces
• Protect from direct sunlight, especially in UAE climates

Unsecured tubing leads to leaks and premature failure.

7. Allow Space for Maintenance
Technicians should be able to:

• Access fittings
• Remove tubing
• Replace valves
• Clean injection quills

Good piping layout simplifies maintenance tasks.

8. Testing and Commissioning the Piping System
Before starting the dosing pump, verify:
Checklist

• No leaks in suction or discharge lines
• Foot valve primed
• Discharge pressure stable
• Back-pressure and relief valves operational
• Calibration cylinder installed (if required)

Testing ensures accurate and reliable dosing from day one.
Correct suction and discharge piping design is essential for achieving accurate chemical dosing and maintaining long-term dosing pump performance. Short suction lines, airtight fittings, proper back-pressure control, pressure-rated discharge tubing, and well-installed injection quills are all critical components of a reliable dosing system. For more info contact Dosing Pump Suppliers in UAE or call us at +971 4 2522966.