Knowledge

This piece of equipment—a Free Chlorine Pocket Photometer—is critical in water testing because it measures the actual disinfecting power currently available in the water.

Here is why this specific device is important for OMFilters compared to other testing methods:

1. It Measures "Free" Chlorine (The Active Sanitizer)

The most important distinction is that this device measures Free Chlorine, not just Total Chlorine.

• Free Chlorine: This is the chlorine that has not yet reacted with contaminants. It is "free" and available to kill new bacteria and viruses instantly.

• Combined Chlorine: This is chlorine that has already "used up" its energy oxidizing contaminants (like sweat or nitrogen). It is no longer an effective sanitizer and causes the strong "chlorine smell" people associate with pools.

• Why it matters: If you only measure Total chlorine, you might think the water is safe when it actually has zero Free chlorine available to protect against contamination. This device tells you exactly how much "killing power" is left.

2. Digital Accuracy vs. Human Error

This photometer is significantly more reliable than standard test strips or liquid "color-match" kits (where you hold a vial up to the light).

• The DPD Method: It uses a chemical reagent (DPD) that turns pink in the presence of chlorine.

• Photometric Reading: Instead of you guessing if the pink matches "1.0" or "2.0" on a color chart, the machine uses a light sensor to measure the exact intensity of the pink color and gives a precise digital number (e.g., 1.43 mg/L). This removes subjective human error.

3. Regulatory Compliance & Safety

For drinking water, food processing, or public pools, maintaining specific Free Chlorine levels is a legal health requirement (usually between 0.2 ppm and 4.0 ppm depending on the application).

• Too Low: Risk of waterborne diseases (E. coli, Giardia, etc.).

• Too High: Can cause skin/eye irritation and create harmful byproducts.

4. Field Portability

Because it is a "pocket" photometer, it allows for lab-grade accuracy in the field. This is essential for immediate decision-making—such as shutting down a water line or adding chemicals immediately—rather than waiting for a sample to be sent to a lab.  This allows for accurate, on-site water testing from OMFilters.

For drinking water treated with chlorine, the goal is to maintain a "residual" level—enough chlorine to keep the water safe as it travels through pipes, but not so much that it becomes harmful or tastes bad.

Here are the specific Free Chlorine targets for drinking water in the United States:

1. The Regulatory "Safe" Range

• Minimum (0.2 mg/L or ppm): This is the widely accepted minimum level required at the "end of the line" (the furthest tap from the treatment plant). If the level drops below 0.2 ppm, there is a risk that bacteria or pathogens could regrow in the pipes.

• Maximum (4.0 mg/L or ppm): The EPA has set the Maximum Residual Disinfectant Level (MRDL) at 4.0 ppm. Water above this level is considered non-compliant and can cause eye/nose irritation or stomach discomfort.

2. The "Ideal" Target

Most municipal water systems aim for a Free Chlorine level between 0.5 mg/L and 1.0 mg/L at your tap.

• At 0.5 - 1.0 ppm: The water is fully protected against re-contamination, but the chlorine taste and smell are usually undetectable to the average person.

• Above 2.0 ppm: Most people will start to smell and taste the "pool water" scent.

3. Why This Matters for Testing

Using the photometer shown in your image is crucial because chlorine is volatile—it dissipates over time and distance.

• If you test at the source: It might read 1.5 ppm (high, to account for travel time).

• If you test at a distant tap: It might drop to 0.3 ppm.

• The Danger Zone: If that distant tap reads 0.0 ppm, the water has no protection left. Any breach in the pipe or backflow could immediately contaminate the drinking water.

If you are local to Los Angeles, send us a message and we would be happy to run some tests on your water.