June 15, 2026
Injection Quills: Design Considerations for Safe and Effective Chemical Dosing
Contributed by Dan Harrington, Applications Engineer
Injection quills are a simple but critical component in chemical dosing systems, designed to safely introduce corrosive or reactive chemicals into pressurized process lines. When properly selected and installed, they protect system components, improve chemical mixing, and extend the life of piping and instrumentation.
What is an Injection Quill?
An injection quill is a specialized fitting that protrudes into the flow stream, allowing chemicals to be injected toward the center of the pipe, avoiding wall contact and promoting thorough mixing. It is commonly paired with metering pumps in water treatment, chemical processing, and industrial dosing systems.
Key Design Considerations
Material Compatibility
Injection quills are available in the marketplace in all Asahi/America piping materials. It is recommended to select materials that are chemically resistant to both the injected substance and the line media. For example:
- Advanced PE (Chem Proline®) for sodium hypochlorite
- PVDF for high purity applications
- ECTFE (Super Proline®) for acids like sulfuric
- Polypropylene for general-purpose water treatment
Size and Quill Length
Quills extend one-third to one-half of the way into the pipe diameter to reach the flow stream. The diameter of the quill will pass through molded components, such as female adapters and flange/stub ends. Both of these diameter dimensions are critical to the design process.
Pressure and Temperature Rating
It’s important to determine an injection quill’s pressure rating so it matches or exceeds the system’s maximum operating pressure. While there are some quills rated for 150 psi or higher, threaded connections can cause limitations if not installed properly. In addition, it’s also important to select an elastomer suitable for the application (e.g., FKM or EPDM).
Retractability & Maintenance
Some quills are fixed, while others are retractable using isolation valves and safety collars. Retractable models are ideal for high-use dosing points, allowing maintenance without depressurizing the system.
Check Valve Integration
Many injection quills will also include a built-in check valve to prevent backflow, protecting dosing pumps and chemicals from contamination.
Common Injection Quill Connection Methods
There are two common types of connections between an injection quill and the pipe into which it’s injecting. The first of these is a threaded connection, where the injection quill has a male thread at its base and is threaded into the sidewall of the pipe. The second is a flanged connection, where the injection quill passes through a blind flange (common in tank connections).
Installation Tips for Injection Quills
- Mount an injection quill perpendicular to flow whenever possible
- Avoid installing injection quills upstream of sensitive equipment or instrumentation
- Label the injection quill with the chemical being injected and the direction of flow for safety compliance
A sparger tube and a peek into how it functions in a tank
Related Components
Sparger Tubes
Sparger tubes are similar tools used to uniformly disperse gases or liquids within tanks, scrubbers, or pipe networks. While not always used in pressurized line dosing, they serve a parallel role in mixing and distributing chemicals—especially in batch or atmospheric systems. Key distinctions between these and injection quills include how sparger tubes:
- Feature multiple perforations or diffusers to promote the formation of fine bubbles or droplets
- Are often used in aeration, pH adjustment, or gas-liquid mass transfer applications
- Can be constructed from the same thermoplastics for corrosion resistance
Sparger tubes are ideal when uniform chemical distribution across a tank is more critical than pinpoint injection into a flow stream.
Dip/Vent Tubes
A dip tube is an accessory that’s typically installed inside storage tanks or chemical feed drums to draw chemicals from specific depths. As such, they must be constructed from materials compatible with the stored chemical and are often reinforced with fins along their length to withstand vacuum suction and thermal cycling. Dip tubes:
- Ensure suction at the bottom of the tank to maximize chemical usage
- Can be paired with foot valves or strainers to prevent debris intake
- Are often used in conjunction with injection quills at the delivery end of a dosing system
Relevant Applications
Common applications for the aforementioned tools and accessories include:
- Sodium hypochlorite injection in potable water systems
- Acid/base neutralization in wastewater treatment
- Coagulant dosing in food and beverage processing
- Anti-scalant injection in reverse osmosis systems
- Uniform chemical dispersion via sparger tubes in neutralization tanks
- Chemical withdrawal from totes/drums via dip tubes in metering systems
Final Thoughts
A properly specified injection quill reduces risk, improves dosing accuracy, and extends system life. Using any standard injection quill on the market, Asahi/America can offer components and design recommendations to adapt injection quills, dip tubes, and sparger tubes into piping systems. Additionally, we can design a system from scratch using a combination of custom and standard components, including multiple materials, sizes, and configurations. Contact our technical team today to help size and select the right solution for your application!