Flow Meter Kit

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 colour change. Once a test strip is reacted, and a colour is developed, the strip is then compared to a printed colour chart. The printed colour chart is specifically designed to represent colour reactions at various concentrations. Matching the strip to the closest colour match produces a concentration reading. Currently, there are no agencies specifically setup to evaluate test strip performance. However, individual manufacturers can solicit independent reviews from several agencies such as the National Science Foundation (NSF) or the United States Environmental Protection Agency (US EPA).

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 American Water Works Association (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 colour block up to the expiration date of the strip. The test strip is put through multiple testing phases and scenarios to see how it performs in real-world situations. After the gruelling testing phase, the data are collected and the results are evaluated. If the test strip meets the desired level of performance, it's accepted and ready for distribution. Competent test strip manufacturers will not release a test strip if its performance doesn't meet the highest possible accuracy and reliability.

Can I use a drinking water quality test strip in my pool or spa?
Generally, it's recommended that you use a test strip that has been specifically designed to work in the water sample that's being testing. Most test strips are designed to test either drinking water quality or pool and 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 colour block. The reason for this is that pool water and drinking water have similar chemical properties. Still, be sure that you are using the right strip for your application to help avoid any inaccurate results.

How accurate are the test strip colour charts?

The colour charts, supplied with test strips, are the most important factors in getting reliable results. The test strip can be the best available but if the strip pad colours don't match the colours printed, then accuracy suffers. To provide the most accurate colour charts available, manufacturers employ tried and true quality control procedures. Beginning with the design work and through the final printing of the colour charts, the quality control staff monitors the process. Quality control members also do a 100 percent 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 colour chart label meet quality control specifications. By employing such a system, test strip manufacturers are able to provide accurate products.

When I use the test strip, I get a colour that isn't on the supplied colour chart. Why does this happen and what does this mean?
Occasionally, a user will get a colour that isn't on the chart. When this happens there are several possible explanations. First, the user needs to make sure the directions were followed closely. When manufacturers develop a test strip and write the directions, the times and procedures provided are written in detail for a reason. Often times, a user didn't follow directions closely, which may result in the strip developing an unusual colour. 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 colour can develop if the sample has a certain level that isn't represented on the colour chart. When a colour chart is developed for a test strip, the manufacturer has to make a couple of choices—what are the common levels encountered in testing for this ion, and what is the separation between the colours, i.e., how distinguishable are the colours from each other. Several different things can cause a colour that doesn't match what is on the colour chart. Commonly, it can mean that the level you are detecting isn't included on the colour chart. Try to extrapolate the concentration of colour for the best estimate. Sometimes when the colour doesn't 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.

Are test strips approved by the U.S. Environmental Protection Agency (USEPA)?
Most test strips aren't USEPA approved; however, there are a few under USEPA evaluation and pending approval. One such strip measures free chlorine. This test strip measures as low as 0.05 parts per million (ppm) and has an accuracy of 97 percent, when compared to an AWWA free chlorine method. Once this strip and others like it are approved, they may be used as reportable screening methods for testing drinking water. This can save time and money. In a home setting, this type of strip is affordable, offers professional quality results and provides consumer confidence.

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's right for you, ask yourself a few questions. First, how long has the company been manufacturing test strips? Experience 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's manufactured by the company? It's 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 isn't as refined as possible. At the same time, companies that only produce test strips focus only on the products they offer. Although this isn't the only indicator of quality, it's 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 the fine details. A great source for this information is to visit the Water Quality Association’s website (www.wqa.org) and search for test strip manufacturers. Fourth, is price representative of the quality? The test strip market is very competitive. Manufacturers go out of their way to make sure the best product is being made available to you at a reasonable price.

I am interested in purchasing test strips. Where should I begin?
Trade publications—whether for the pool & spa industry or point-of-use/point-of-entry water treatment industry—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. And always make sure you evaluate these samples under typical use conditions.