Inaccurate test results are not always the fault of the water-testing equipment or because something in the water’s chemistry is interfering with the test. Sometimes incorrect techniques, sample contamination or incomplete cleanup can be to blame. But the good news is you can easily rectify those situations with proper guidance and a little extra care.
Follow the Instructions Every Time
When you test your water regularly, it may be easy to assume that you know what you’re doing and you don’t need to read (or re-read) the instructions. But reading the instructions is always a good idea. First, there are important differences between tests and testing product brands. Even if it is the same test equipment from the same manufacturer, an important procedure may have changed. All testing supplies, including even the simplest test strips, have specific techniques required for success. Stay informed by reviewing the instructions before use.
Collect a Representative Water Sample
Test results are used to make treatment decisions; if the sample collected does not represent the conditions of the whole pool, your results will be inaccurate and result in improper treatment.
To obtain a good water sample, always:
-
Use a clean sample container.
-
Avoid sampling water near return lines, chemical feeders or in dead zones like steps and corners.
-
Take your sample near the midpoint of the pool at the specified depth.
Test Immediately and Time Reactions Precisely
Do not allow a water sample to sit for any length of time after taking it. The sanitizer residual is particularly likely to change if the sample is allowed to sit, resulting in a false-low reading. If instructed to observe a wait time after adding reagent(s) – do not omit this step. Several tests need extra time for proper color development, including multiparameter test strips, so it’s important to read the test results in the order specified.
Note: After adding a treatment chemical, allow at least two filtration cycles to pass before re-testing to allow the product added to properly circulate throughout the pool.
Measure Sample Volume and Reagents Accurately
Carefully measure the sample volume and be sure to add the correct amount of reagent. Sometimes even a slight variance in either one can have a major impact. Here are some basic rules to follow:
-
When using a dropper bottle to dispense reagent, always hold the bottle in a vertical position.
-
Do not allow static buildup on the dropper tip which could reduce the size of drops or amount of reagent dispensed.
-
Completely incorporate any reagent powders or tablets, being especially vigilant when using square test vials where reagent can get stuck in the corners.
-
If using a pipet, be sure to check for air bubbles to avoid improper measurement.
Use Proper Lighting for Color Matching
Most manufacturers recommend doing color-matching tests outdoors in natural light (but don’t look into the sun). Artificial lighting can skew color perception and so will wearing sunglasses. Colorimeter users need to be aware that stray light can interfere with a test, so it’s important to close the lid or cap on the sample chamber as directed.
Prevent Contamination at Every Step
Here are some tips to help avoid contamination:
-
Thoroughly rinse and dry sample containers, test cells and caps to remove any residue from a previous test.
-
Do not switch caps between reagent bottles or place them on an unclean surface.
-
Do not use your finger to cap a test cell when swirling a sample to incorporate reagents or allow your finger to touch the pads on a test strip.
When in doubt, stay focused! Paying close attention to what is happening throughout each test is the key to success.