This article intends to clear things up in providing important guidelines and considerations when testing for water quality.
The quality of water necessary for its many different uses is as diverse as the uses themselves. Water that is good quality for swimming is not suitable to drink (potable), watering plants or cleaning food. Ground (well) water will have different parameters than Municipal (city) water.
The intended use of water determines which testing and treatment is needed. With the advancement of technologies, testing water quality can be done quickly.
Laboratory quality results that once took weeks can now be done in mere minutes onsite. Basic testing and maintenance of swimming pools is required to protect swimmers and bathers from disease and infection. The primary goal is to produce aesthetically pleasing water that makes the pool look good and inviting.
Accurate testing results support correct maintenance that ultimately saves your institution time and money. Pool water quality testing sounds like a daunting task, but can be easily done with proper training and scheduling.
Pool Parameters to Test
Out of the four major parameters in the pool that should be tested, Chlorine is the most important. It is the primary chemical found in most pools and the most common sanitizer.
In fact, Chlorine is the most popular sanitizer, disinfectant, algae killer, and oxidizer in the world. Inexpensive and safe when used properly, Chlorine is very effective against a broad range of microorganisms. Monitoring chlorine concentrations are very important for a healthy pool. State Health Departments require pools to be routinely tested for chlorine concentrations.
The difference between Free, Combined and Total Chlorine are frequently misunderstood.
- Free Chlorine is the chlorine that is still available to sanitize your pool water.
- Combined Chlorine is the chlorine that has already been “used up” from sanitizing your water.
- Total Chlorine is the sum of the Free and Combined.
Test the Free Chlorine levels multiple times daily depending on the amount of swimmers. High Free Chlorine levels can cause eye and skin irritation. Low Free Chlorine levels can cause illness and disease. Desired level: 2.0-4.0 ppm.
pH is the unit of measurement used to determine if the water is acidic or alkaline (basic) and influences effectiveness of sanitizers and oxidizers. pH ranges on a scale of 0-14, where 0 is most acidic and 14 is most basic. The higher the pH level in your pool or spa, the less effective chlorine is as a sanitizer. pH that is out of range can cause damage to pool hardware and fittings, and cause sick swimmers. Desired level is between 7.4 – 7.6 pH.
Total Alkalinity is the water’s ability to resist change in pH, or the waters “buffered capacity.” Low alkalinity can lead to pH bounce (rapid variations in pH) while high alkalinity can lead to pH being very difficult to change. Desired level is between 80-120ppm.
Calcium Hardness is the amount of calcium in the water. Low calcium can lead to pitting of eroding of pool surfaces, while high calcium can lead to calcium deposits and cloudy water.
The recommended level of calcium will vary based on the temperature of the water sample as calcium’s saturation gets lower the higher the water temperature. Desired level is between 200-400ppm.
Methods for Testing Water Quality in Pools
There are four methods used for testing in the pool industry.
1) Digital Photometer – Mostly handheld, these units use different reagents (liquid, powder, tablet, or reagent strip) to measure water quality. A digital instrument measures reacted color by passing light transmission through a water sample. Concentration is determined by the amount of light that is transmitted through the reacted sample. It’s the most accurate and reliable method.
2) Colorimetric titration – Involves counting drops and matching color, using liquid and powder reagents. This is a popular test method.
3) Comparator color test – Uses liquid, powder, tablet, or reagent strip with a test tube or comparator color chart scale.
4) Test strips – Involve visual matching to a color chart scale after dipping. Strips are inexpensive and a good screening method, but have the least accurate results.
What testing method is best for your aquatic facility needs depends on a variety of factors. Cost is an important consideration. Tests can vary from $0.02 to $0.30 up to $10 per test. Time is money; so, consider the time to complete each test. Staff should be comfortable running the tests; therefore, it should be easy to use and determine the results. Most importantly, the chosen test method should meet State Health Department compliance testing requirements.
Best Practices for Pool Water Quality Testing
Before any testing, read and understand the test procedure and follow manufacturer’s test directions carefully.
For the best photometric results: Collect the sample water 18 inches below the surface at elbow length. After collecting a water sample, perform tests quickly.
When using test strips: Pay close attention to expiration dates printed on the bottle . Match visual test results under the right conditions with proper lighting; for example, don’t match colors in bright sunlight or when wearing sunglasses.
For titration and comparator tests: Add the liquid reagents carefully, making sure the correct number of drops are added to the sample and the drops are equal and full-sized. Store liquid reagent containers tightly capped and in a cool, dark place. When testing is finished, never dispose tested samples or reagents in the pool.
Using these testing parameters, methods, and best practices in ensuring good water quality will clear things up while making your campus safe.