Available chlorine is one of the most critical indicators in water quality control. Whether you are managing drinking water, wastewater, industrial processes, swimming pools, or aquaculture systems, accurately testing for available chlorine is essential to ensure safety, compliance, and effective disinfection.
In this article, we explain what available chlorine is, review the most common testing methods, and introduce a reliable portable solution—the ERUN-SP7 portable multi-parameter water quality tester—for fast and accurate on-site chlorine measurement.
Available chlorine refers to the portion of chlorine in water that is chemically active and capable of disinfecting microorganisms. It generally includes free chlorine (hypochlorous acid and hypochlorite ions) and combined chlorine (chloramines), depending on the testing method used. In practice, available chlorine is often assessed through residual chlorine or total chlorine measurements.
Chlorine is widely used as a disinfectant because of its effectiveness and low cost. However, insufficient available chlorine may lead to microbial contamination, while excessive chlorine can cause corrosion, unpleasant taste and odor, and health risks. Accurate available chlorine testing is therefore essential for:
l Drinking water treatment and distribution
l Wastewater disinfection
l Industrial process water control
l Swimming pools and recreational water
l Aquaculture and environmental monitoring
The DPD (N, N-diethyl-p-phenylenediamine) colorimetric method is the most commonly used technique for testing available chlorine. Chlorine reacts with the DPD reagent to produce a pink or red color, and the intensity of the color corresponds to chlorine concentration.
Advantages:
Fast and easy to use
Suitable for portable instruments
Good accuracy for routine monitoring
Limitations:
can be affected by turbidity or color
Requires proper reagent handling
Iodometric titration is a classical laboratory method used for high-accuracy chlorine analysis. Chlorine oxidizes iodide to iodine, which is then titrated with sodium thiosulfate.
Best suited for:
l Laboratory reference testing
l High-concentration chlorine samples
However, this method is time-consuming and not ideal for on-site measurements.
Compared with visual test kits, portable chlorine testers offer higher precision, digital readings, and better repeatability. They are ideal for field testing where speed, accuracy, and data reliability are critical.
l Free chlorine: Most effective disinfectant form
l Total chlorine: Free chlorine + combined chlorine
l Available chlorine: Indicates overall disinfecting capacity
Choosing the right parameter depends on regulatory requirements and application scenarios.
Other water parameters can influence chlorine measurement and effectiveness, including:
l pH
l Turbidity
l Color
l COD
l Ammonia nitrogen
Measuring these parameters together provides a more complete picture of water quality.
A reliable, available chlorine tester should offer:
l High measurement accuracy
l Low repeatability error (≤3%)
A stable optical system with minimal drift
These factors ensure consistent and trustworthy results in long-term monitoring.
Modern water analysis often requires testing multiple parameters. A multi-parameter water quality tester reduces equipment costs, improves efficiency, and supports comprehensive water management.
The ERUN-SP7 from Erun is a portable multi-parameter water quality tester designed for accurate and on-site analysis. It supports testing of residual chlorine, total chlorine, and chlorine dioxide, making it highly suitable for available chlorine monitoring across different applications.
Beyond chlorine, ERUN-SP7 can measure a wide range of parameters, including:
l COD
l Ammonia nitrogen
l Total phosphorus
l Total nitrogen
l Turbidity and color
l Copper, chromium, manganese, iron, zinc, aluminum
l Cyanide, phosphate, sulfate, nitrite, and hardness
The instrument can also be expanded and customized according to user requirements, covering heavy metals and inorganic salts.
Key performance highlights include:
l Repeatability: ≤3%
l Optical stability: Absorbance drift <0.002A within 20 minutes
l Reading modes: Concentration, absorbance, and light transmittance
These features ensure stable, accurate, and flexible chlorine testing in both field and laboratory environments.
Contact us today to get detailed specifications or request a quotation:
Email: stella@xayingrun.com
WhatsApp:（+86-18189135710）
Available chlorine testing ensures disinfection efficiency and regulatory compliance throughout water treatment processes.
Accurate chlorine control protects public health, aquatic life, and ecological balance while preventing over-chlorination.
The best way to test for available chlorine is by combining a reliable colorimetric method with a high-quality portable instrument. The ERUN-SP7 portable multi-parameter water quality tester offers accurate chlorine analysis, excellent optical stability, and extensive parameter coverage, making it a dependable solution for professionals.
For users seeking accurate, efficient, and customizable chlorine testing, ERUN-SP7 from erunwas.com is a smart and future-proof choice.
