How do test strips work?

How accurate and reliable are test strips?

How accurate are the test strip color charts?

Are test strips US EPA approved?

When I use the test strip, I get a color that is not on the supplied color chart. Why does this happen and what does this mean?

Can I use a drinking water quality test strip in my pool or spa?

Which test strip brand should I use?

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How do test strips work?

Test strips are small strips, typically produced from plastic "sticks", with chemically impregnated pads on the end. These pads are designed to react with specific ions and produce a specific color change. Once a test strip is reacted, and a color is developed, the strip is then compared to a printed color chart. The printed color chart is specifically designed to represent color reactions at various concentrations. Matching the strip to the closest color match produces a concentration reading.

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How accurate and reliable are test strips?

Test strips can be quite accurate. Most manufacturers utilize several industry-standard reference methods to compare and calibrate their strips. One of the most comprehensive collections of reference methods is contained in the AWWA manual for water and wastewater treatment and evaluation. Once the standard reference method is established, the test strip manufacturer determines the level of accuracy that the strips should meet; generally the accuracy is within a color block up to the expiration date of the strip. The test strip is put through multiple testing phases and scenarios in order to see how it performs in real-world situations. After the grueling testing phase, the data is collected and the results are evaluated. If the test strip meets the desired level of performance, it is accepted and ready to be sold. Competent test strip manufacturers will not release a test strip if its performance does not meet the highest possible accuracy and reliability.

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How accurate are the test strip color charts?

The color charts, supplied with the test strips, are the most important factor in getting reliable, accurate results. The test strip can be the best available, but if the strip pad colors do not match the colors printed then strip accuracy suffers. In order to provide the most accurate color charts available, manufacturers employ tried and true quality control procedures. As an example, Industrial Test Systems, Inc., manufacturer of the SenSafeTM and WaterWorksTM line of test strips, takes a very active role in test strip color chart printing. Beginning with the design work and through the final printing of the color charts, the quality control staff monitors the process. Quality control members also do a 100% check of all printed labels before use. Before the test strips are shipped, the labels are checked once again to make sure that the test strip lot and color chart label meet quality control specifications. By employing a system such as this, test strip manufacturers are able to provide accurate products.

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Are test strips US EPA approved?

Most test strips are not US EPA approved. However, there are a few that are under US EPA evaluation and pending approval. One such strip measures Free Chlorine. The Free Chlorine Water CheckTM test strip measures as low as 0.05 ppm (parts per million) and has an accuracy of 97%, when compared to an AWWA free chlorine method. Once this, and other test strips like it, is approved, they may be used as reportable screening methods for testing drinking water. This can save not only time, but also money. In a home setting, this type of strip is affordable and offers professional quality results that you can be confident in.

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When I use the test strip, I get a color that is not on the supplied color chart. Why does this happen and what does this mean?

Occasionally, a user can get a color that is not on the color chart. When this happens there are several possible explanations. First, the user needs to make sure that the directions were followed closely. When manufacturers develop a test and write the directions, the times and procedures that they provide are written in detail for a reason. Often times, a user did not follow the direction closely which may result in the strip developing an unusual color. To avoid this, make sure that you carefully read and follow the directions. Also, keep in mind that while most test strips look similar, the directions for the strips can be very different. This can be true even when dealing with test strips from the same manufacturer. Second, an unmatchable color can develop if the sample has a certain level that is not represented on the color chart. When a color chart is developed for a test strip, the manufacturer has to make several choices: (1) what are the common levels encountered in testing for this ion, and, (2) what is the separation between the colors – how distinguishable are the colors from each other. Several different things can cause a color that does not match what is on the color chart. Commonly, it can mean that the level you are detecting is not included on the color chart. Try to extrapolate the concentration of the color for the best estimate. Sometimes when the color does not match at all, this can be caused by interference ions in the sample. When this occurs, contact the manufacturer to see if another, more appropriate test is available.

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Can I use a drinking water quality test strip in my pool or spa?

Generally, it is recommended that you use a test strip that has been specifically designed to work in the water sample that you are testing. Most test strips are designed to test either drinking water quality or pool & spa water quality. When an incorrect water sample is tested using a water quality test strip, the results can often still be acceptable. As an example, if a water quality Free Chlorine test strip is used in pool water, the results will more than likely be correct to within a color block. The reason for this is that pool water and drinking water have similar chemical properties. However, be sure that you are using the right strip for your application in order to help avoid any inaccurate results.

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Which test strip brand should I use?

There are several test strip brands currently available on the market. When choosing the test strip company that is right for you, you should ask yourself a few questions. First, how long has the company been manufacturing test strips? Length of time can be a good indicator of expertise and knowledge in the market. Traditionally, the longer the manufacturer has been in business, the more reliable the test strips offered. Second, are test strips the only product that is manufactured by the company? It is best to go with a company whose major focus is test strips. Companies that produce a wide variety of products can often provide a test strip that is not as refined as possible. At the same time, companies that only produce test strips focus on the products that they offer and make sure that they are the best. Although this is not the only indicator of quality, it is a good place to start. Third, what brand are others in my field using and what is their opinion? Peer recommendations can be a great source of information because they have already been through the task of looking at all of the fine details. Fourth, is price representative of the quality? The test strip market is very competitive. Manufacturers go out of their way to make sure that the best product is being made available to you at a reasonable price.

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I am interested in purchasing test strips. Where should I begin?

Trade publications are often a great place to look for available test strips. Most test strip manufacturers advertise on a regular basis. Once you have composed a list of the manufacturers contact each one and request some free samples. A test strip manufacturer that believes in their products will be more than happy to provide samples. Make sure you evaluate these samples under the typical use conditions.