As a service technician charged with insuring the safety of bathers, you simply must have an accurate handle on the condition of the water in your pools and spas.
Just because you stop by once a week to add a gallon of liquid — or feed the feeder with a couple of tabs — doesn't mean that the pool or spa is in proper balance.
It's entirely possible that bather load has been so low that your sanitizer level is now too high. Your pH reading may also be out of whack. Other chemical imbalances in the water can have a huge effect on sanitizer level, water clarity, pool equipment and pool surfaces.
In fact, professionals know that there are at least 10 different things you may need to test for to truly understand what is happening in the water.
The obvious is sanitizer level and pH. But a poor alkalinity level can cause your pH to bounce all over the comparator chart. Add to those cyanuric acid level, hardness, TDS, copper, iron, nitrates and temperature, and you've got quite a handful.
Fortunately, modern service professionals have several choices available to them when it comes to testing methods. Basically, they can be broken down into five major groups:
With this in mind, we've again sought out the able of assistance of test-kit manufacturer Taylor Technologies. Following is a series of questions and answers the company has prepared that can help you increase your knowledge about water testing and testing accuracy: My test results indicate there is no chlorine in the pool, but I know there is. Why does this happen?
This is usually an indication of too much chlorine in the water, causing the DPD to bleach out. To develop a readable color, dilute the sample and repeat the test. Multiply the result by the appropriate factor: for a 1:1 dilution, multiply the result by 2; for a 1:3 dilution multiply by 4, etc.
My sample water turns cloudy when I add DPD #1. Will the test still work?
Yes. A sample usually turns cloudy when DPD # 1 is added to water with high levels of hardness that precipitated out as calcium and/or magnesium salts. The cloudiness will not affect your test results and should disappear when you add DPD #2. To avoid cloudiness entirely, add the sample water to test cell already containing 5 drops of each DPD #1 and DPD #2.
Why aren't my free and total chlorine readings different when I know I have chloramines in the water?
When this happens, a small amount of DPD #3 was probably left in your test cell from as previous test. Even a trace amount of DPD #3 will interfere with a free chlorine test, leaving you with a total chlorine reading. Therefore, it is very important to clean the test cell after each use.
Can I use a bromine comparator to test a chlorine-sanitized pool, and visa-versa?
Yes. DPD undergoes the same chemical reaction with bromine as with chlorine, but the color intensities produced are different. To convert from bromine to chlorine, simply divide the value on the bromine comparator by 2.25. If a chlorine comparator is used to test a bromine-sanitized pool, multiply the result by 2.25 to determine ppm bromine.
Why do I sometimes get a blue/purple instead of a yellow-to-red color when using phenol red indicator?
This occurs when the chlorine level in the pool is too high (usually greater than 5.0 ppm). To eliminate chlorine interference, add 1 drop of chlorine neutralizer (thiosulfate) before adding the indicator solution.
When I add my total alkalinity reagent, I get a yellow endpoint instead of a red endpoint. Has the reagent gone bad?
No. Your reagent is producing a yellow endpoint due to an excess of chlorine in the sample. Add an extra drop of thiosulfate reagent to the sample to remove the chlorine interference.
I got a purple endpoint instead of a blue endpoint when I did a hardness test. What happened?
There are metal ions interfering with the test, most likely copper ions from algicides, pipes or even the water itself. To avoid this problem, add a few drops of titrant to the sample before adding the buffer and indicator, then proceed normally with the test. Always include the number of drops of titrant added at the beginning of the test when counting the total number of drop required to reach endpoint.
Can I use other manufacturers' reagents with my Taylor Slides, Midgets or other comparators?
No. Each manufacturer makes its reagents in different concentrations, and the color standards are developed for a specific reagent concentration. For example, Taylor produces several phenol red solutions, including R-0004 pH Indicator Solution and R-1003J Phenol Red Indicator. If R-1003J Phenol Red Indicator is used with a comparator developed for the R-0004 pH Indicator Solution, the colors will have the wrong intensity, and your readings will be inaccurate. There is one exception to this rule — DPD liquids and tablets can be easily interchanged in most color-matching tests.
Why are there different test cells, and can they be used interchangeably?
Different test cells cannot be used interchangeably. Taylor has designed test cells of different viewpaths to accommodate variable concentrations. Generally, we use a 1-cm viewpath (#4025) for comparators with values from 0-10 ppm, while a 2.3-cm viewpath (#4024) is used for more sensitive values between 0-3.0 ppm. For trace analyses (0-0.3 ppm), Taylor has a 15-cm viewpath test cell (#9018). There are exceptions to this rule, so you may need to check with a manufacturer's technical staff before choosing a test cell for your comparator.
When doing a drop test, can I change the reagent's equivalence from the standard given?
Sometimes. To change the equivalence of a drop test, you must change the sample size proportionally to the desired change in equivalence. For example, if the standard equivalence for the test is 10 ppm using a 25-ml sample, you would need a 50-ml sample to obtain a 1 drop = 5 ppm. Likewise, a 12.5-ml sample would give results as 1 drop = 20 ppm. Again, you may want to contact a manufacturer's technical staff before changing the equivalence of any test.
What is the shelf life of my reagents?
Different reagents have different shelf lives. Because of this fact, storage conditions play a major role in determining the “freshness” of any reagent. As with most perishables, reagents must be stored under controlled environmental conditions. We prepare our liquid reagents to remain fresh for at least one year from the date of manufacture. In addition, powders and crystals have unlimited shelf lives. Listed below are some simple rules to help preserve your reagents:
By following directions and guidelines, you can be sure that you are doing what is needed to maintain safe conditions for your customers and balanced water for your pools and spas.