Pool Info: Pool Test Strips FAQ
Do test strips really work?
Yes. Test strips were developed in the medical diagnostic industry in the 1960's. Since that time, they have replaced liquid reagent tests for urine and blood testing. Swimming pool test strips use that same technology.
How accurate are test strips?
Test strips are at minimum comparable in accuracy to liquid color comparator tests. Because test strips are more convenient, we believe they can sometimes deliver greater accuracy. They reduce the chances of human error associated with liquid kits, which require measuring samples and counting drops of reagent.
What supports the accuracy of test strips?
AquaChek test strips are manufactured and released against standard reference procedures from the 17th Edition of Standard Methods for the Examination of Water and Waste Water.
Is a DPD liquid pool tester more accurate?
The DPD test for chlorine can be affected by interferences, such as an overabundance of mono-chloramines or potassium mono-persulfate (used for shock-treating pools). These can give a false positive reading for free chlorine with the DPD chemistry. In addition, the DPD test requires careful technique and several steps to obtain the best test results. Some of the better test strips will test for Free, Total and Combined chlorine, just as the reagent style of dropper bottle test kits do.
Can more values for each test be added to color charts?
There would not be enough color differentiation between the values. This would make it difficult for the user to make a decision when comparing the test strip to the color patches on the label.
What is the difference between AquaChek and the other pool and spa test strips available on the market?
AquaChek is the top-selling brand of pool and spa test strips in the world. AquaChek test strips undergo stringent release qualification. Constant monitoring of the manufacturing process ensures that the finest test strips are available for your use.
Do I need to test as frequently with test strips?
Yes. We suggest testing both ends of the pool a minimum of 2 times a week, and spas before each use.
Are test strips less accurate after the expiration date?
If the test strips are handled and stored properly, they should give reliable results through the expiration date on the bottle label. It is impossible to determine how reliable the results will be after the expiration date has passed. Store in a dry, cool location, and always keep the container tightly capped to lock out moisture.
Are digital test strip readers more accurate?
Yes, in that it removes the glare and visual interpretation from the calculation. Digital readers measure the color on the test pad with a color contained in a database of over a million colors, to produce more accurate results than humans.
What testing method should you use?
You don’t have to be a chemist to keep your pool sparkling clean. To keep things simple, use a testing method that you find fast, easy and convenient. That way you’ll be more likely to stick to your testing regimen. There are two basic types of testing method used by most consumers: test strips and liquid kits.
Liquid test kits
Liquid kits require that you put a sample of water into a plastic comparator and then carefully add drops of chemical reagent, watching for a change in the color of the sample. Liquid test kits with the reagent OTO were once widely used to measure chlorine, but they have fallen out of favor in recent years. OTO measures only total chlorine, not free chlorine, which is the form of chlorine most effective in sanitizing your pool. In addition, we now know that a chemical reagent in the OTO-type kit has been shown to be mildly carcinogenic.
Test Kits using the liquid reagent known as DPD do measure free chlorine. However, if you test for free chlorine using a DPD #1 liquid test kit, be aware that high levels of combined chlorine, or chloramines, can cause false-positive results when testing free chlorine. Substances such as monopersulfate (used for shock-treating pools) can also affect the results of the DPD test by causing a false positive reading. Used properly, DPD kits and especially FAS-DPD kits, can give excellent results.
Test strips, the easiest method for pool and spa water testing, are fast and simple to use because they eliminate the need to measure samples and count drops. Typically, you simply dip a strip in the water for one second and then remove it. You then compare the color on the strip to the color chart on the label.
Industry and water quality experts report that test strips are comparable in accuracy to liquid kits. In fact, many believe they actually deliver greater accuracy than liquid kits because they require less technique. In other words, it’s hard to screw up a test strip test.
Many local and state health departments now recognize AquaChek test strips as an approved testing method. This means that professional pool and spa service technicians as well as other industry experts trust the accuracy of AquaChek pool and spa test strips.
Today, there are reliable test strips available to test a wide variety of pool conditions, including cyanuric acid and total dissolved solids as well as free chlorine, pH and total alkalinity. There are test strips for metals, bacteria, salt and phosphates.
No matter what type of test kit you decide to use, be sure to follow the manufacturer’s recommendations to get the best results. If you have access to a pool store that does water testing, you can compare your own test results to gauge accuracy of your pool test method.
Other Methods to Obtain Greater Accuracy in pool water testing include:
- Use Fresh Reagents, most have a shelf life of 1 year.
- Test strips typically have a 24-36 month shelf life. Look on container bottom for expiry date.
- Store reagents and test strips in a cool, dry location, out of direct sunlight.
- Take your water sample or dip your strip under the surface, so as not to test surface water.
- Keep your testing vials clean and rinse them well between tests.
- If you test gives an unusual result, test again to be sure before chemical adjustment.