Why a Water Test Kit Can Make a Difference
What is a home water test kit?
Home water test kits come in a variety of methods, styles, and shapes. They include simple test strips that you dunk in the water and swirl around for a few seconds and then compare the test strip colors to the colors on the side of the bottle. Test kits also include chemical titration tests that work for hardness and iron, a photometer, or a TDS electronic handheld meter that test for total dissolved solids (TDS) and pH or ORP (oxidation reduction potential).
Typical low-tech, portable, field test methods for chemical water quality monitoring fall into three categories:
- Test strips – These are small, single-use strips that change color to indicate the concentration of a specific chemical. Depending on the particular test, the user “activates” the paper or plastic strip by dipping it into the water sample and swishing it around, or by holding the strip in a stream of water. After waiting for a short time, the user compares the test strip color with a color chart to read the concentration of the chemical. These kits are extremely simple, but they are less accurate than other methods, especially if users don’t follow the instructions.
- Color disk kits – Color disk test kits are available for a wide range of chemical tests. In a typical set-up, the user adds a powder packet or a few drops of a liquid reagent to a water sample in a reusable plastic tube. The user then places the sample tube in a small plastic viewing box. This viewing box contains a plastic disk with a color gradient printed on it. The user rotates the color disk to find the part that best matches the color of the sample, and then reads the concentration of the chemical from the disk. Color disk kits typically have multiple steps and often include prescribed wait times, so they’re a little more complicated and costly, but generally more accurate.
- Hand-held digital instruments – Lightweight and portable digital meters, colorimeters, and photometers are available for water testing. They provide the most accurate results of these three testing methods, but they are also more expensive and delicate than the previous options. These instruments require batteries and calibration. While digital instruments are helpful to field technicians and are an essential part of any continuous or remote monitoring network, they are unlikely to be suitable for “citizen science” or crowdsourced water quality testing.
What is the best way to test water quality for your purpose?
- Biological Indicators
Biological monitoring metrics is the simplest and least expensive method. It involves monitoring the presence and abundance of members of bio-indicators common to the area, eg:
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Insectssuch as the mayfly, stone-fly and caddisfly. Generally, the greater the number found, the better the water quality. Organisations in the United States, such as EPA offer guidance on developing a monitoring program and identifying members of these and other aquatic insect orders.
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Bivalve molluscsare largely used as bio-indicators to monitor the health of aquatic environments in both fresh water and the marine environments. A typical project is the Mussel Watch Programme, but today they are used worldwide.
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Benthic macro-invertebrates (such as the aquatic earthworm) is a bio-monitoring tool that is used by the Southern African Scoring System (SASS) system to measure river health. miniSASS is a simpler scoring system that can be used by anyone, even school children.
- Test Strips
Test strips for various water quality parameters are available, such as pH, chlorine, etc. Here you dip a little paper strip with graduated colours into your water sample and match it with a colour on a printed list, to determine the level of the parameter.
Test strips are inexpensive, quick and easy to use, but offer the least accuracy and precision, due to printing variations, poor resolution and the variability of the human eye.
- Titration / Drop Test Kits
This simple method uses visual titration. A chemical (reagent) is added to a water sample and the concentration is then determined by counting the number of reagent drops or tablets required to induce a colour change.
It offers higher accuracy than test strips, but involves some technical ability, because careful counting, basic calculations and and the ability of the human eye will be required. It is a rapid, economical test for all chemical parameters, such as pH.
The exception to the rapidity of the testing are microbiological tests, such as those for coliform / e.coli. These require incubation for 12 – 48 hours.
- ATP / Luminescence Tests
A luminometer and a consumable testing device can be used to instantly measure the presence or absence of bacterial contamination in water. It is ideal for quick screening, but more in-depth and time consuming testing will need to be undertaken if more detail is required.
- Electro-Chemical Testers
These testers comprise of a pen-type, hand-held or bench-top meter and an electrode. They are very useful for in-the-field / in-situ testing and are usually rugged and waterproof. However, the electrode needs to be carefully maintained and will need to be replaced every few months to few years, depending on circumstances.
Only a few key parameters can be measured in this way, such as pH, electrical conductivity, dissolved oxygen, total dissolved solids and salt. The many other water quality parameters will need to be measured using another method
- Colorimetric / Comparator Test Kits
Colorimeters or comparators have been widely used by companies for well over 100 years, to measure the quality of water. A reagent is added to a known sample of water. The intensity of colour is then compared with coloured plastic or glass filters, in order to see the concentration of chemical present in the water (eg. Chlorine).
- Photometric Test Kits
The most popular option today is the modern electronic photometer. This is the easiest and most accurate way to test water, if you are performing frequent water testing, or require precise results.
- Spectrophotometers
For specialised water testing that requires many parameters to be tested with the highest precision levels, a spectrophotometer is the ultimate instrument.
This instrument features a dual beam optical system, one of which is reference beam, for above average accuracy. UV light and / or visible light can be used. Further functions can include measurement of transmission and absorbance, scanning of spectra and kinetics analysis.
Five Sources Of Error In Water Testing…And What To Do About Them
- The sampling location
Take a sample of water that is representative of the whole pool or spa—not from the surface, which is subject to special conditions, and not in the immediate vicinity of a return line for the same reason. For pools, sample midway between the shallow and deep ends. Use a clean plastic bottle. Insert it bottomside up so the trapped air keeps out the water momentarily, and then turn it rightside up when you get to elbow depth and let it fill.
- The operator
It may seem obvious, but experience shows people still need to be reminded to read the testing instructions completely before beginning to test. You should do this: A) whenever you buy a replacement test kit or bottle of strips, just in case the manufacturer has changed something in the procedure, and B) whenever you buy a brand for the first time because manufacturers’ products all are a little different, including our test strips. You should continue to read over the instructions before starting the tests until you are completely familiar with each step.
- The lighting
Doing color-matching tests in artificial light, or with your sunglasses on, is a no-no. You can buy an inexpensive, portable daylight simulator, like photographers use, if you must read colorimetric tests indoors. Some countertop testing stations have these daylight lamps already built in.
Use your meter’s light shield to prevent stray light from interfering with test results.
- The water chemistry
If you’ve just treated the water, wait to retest until the proper amount of time has elapsed (as specified by the treatment chemical manufacturer, typically at least one turnover (typically 6‒8 hours).
There also could be interferences in the water that cause the wrong color to develop, or no color to develop—for example, a high level of sanitizer, the presence of a monopersulfate-based oxidizer, or metal such as copper from an algaecide or iron from your fill water. The best testing products tell you what to do in these cases. Call for technical support when in doubt.
- The testing tool
Buy equipment from a reputable manufacturer. With that caveat, these other sources of error are easily remedied.
Most test methods are limited by an operational range. Testing a parameter outside of the range specified by the manufacturer means the results cannot be interpreted correctly. For instance, chlorine over ≈10 parts per million (ppm) and bromine over ≈20 ppm may partially or completely bleach out the pink color of a conventional DPD color-matching sanitizer test. In this instance, one can dilute the sample and retest to obtain an approximate sanitizer value. But dilution is not always the answer. For example, a high level of either chlorine or bromine can also cause the pH test and the total alkalinity test in both liquid kits and test strips to give false readings. Here, one must wait until the sanitizer level returns to normal to retest. Another example is phenol red. Whether used as a liquid reagent or on a test strip, this indicator only works between pH 6.4 and 8.4. If the pH of a sample is beyond this range, use another test method (e.g., an electronic meter or another indicator that will test as high, or as low, as needed), or retest, this time adding 1 drop Thiosulfate N/1 (R-0007) to the sample first if using a 2000 Series™ comparator or a sureCHECK™ test kit comparator.
Verdict: Which is the Best Water Test Kit?
Home water test kits have their limitations, and they’ll never be as accurate as tests performed in professional labs.
But, they can be helpful as a first step toward diagnosing problems with your drinking water.
If there’s any indication that your water is not safe, you should always follow up with a professional test.
Sure, you can buy more expensive home test kits that will test for a greater variety of contaminants. But, they’re still going to be much more prone to human error than testing done in a lab.
And, if you’re going to spend $100+ on a home test, why not just have a professional do it instead? You could probably get testing done by your state health department for less than the cost of one of the fancy home test kits for sale online.
So now that we’ve taken a closer look at these test kits and tried them out, the question is which one is the best?
In terms of overall accuracy, I’d say it’s a toss up between First Alert and Watersafe.
If you have well water, I’d recommend the Watersafe Well Water Test Kit because it tests for iron and copper in addition to the other basics.
But if you’re on city water, you could go with the First Alert Water Test Kit.