For many of us, the backyard swim pool is the centerpiece of our summer days.
Whether that means cooling off with our feet dangling in the water, working it out with some water aerobics classes, or getting fired up with an impromptu game of water volleyball with friends and family, the pool is where the fun happens.
But first, your pool, and more importantly, the pool water, needs to be ready for action.
Which means testing!
Using a pool test kit regularly helps maintain a healthy pool, avoiding the spread of bacteria, algae, and even protecting your pool equipment.
A lot of new pool owners feel intimidated by testing pool chemistry, believing that there is too much to learn or that properly balancing pool water is impossible without professional help.
But using a pool test kit is actually quite straightforward, and once you get a quick lay of the land (or rather, the water), you will quickly feel comfortable testing your pool as part of your regular cleaning and maintenance schedule.
This article lays out everything you need to know about the almighty pool test kit, including the different types, how often to test, and much more.
Let’s jump right in.
1. What is a pool test kit and what does it do
The pool test kit is something that helps you to maintain the chlorine and pH levels in your pool. Done weekly, your swimming pool will remain sparkling and clean.
The purpose of the test kit is to determine if your water chemistry needs adjustment, which can be done by adding chemicals or minerals. While the main things you want to test for are the chlorine and pH levels, test kits also give an overview of cyanuric acid, calcium, phosphate, copper, and salt levels.
Test kits help you ward off a lot of problems that can happen with the structural parts of your swimming pool, too.
When the pH, alkalinity, and hardness of the pool water are off, corrosion soon follows with the pool liner, filtration equipment, or even the walls of the pool.
Test kits are your best friend when it comes to swimmable water and extending the lift of your swim pool and equipment.
2. What are the different kinds of pool test kits?
While you can take a water sample and take it down to your local pool store to have it professionally tested, there are plenty of affordable and accurate pool test kits that pool-owners can use at home.
Here are the main types to look out for:
- Liquid test kits. Very common and they cover much of the pool owner’s needs for testing. They last quite a while, around a year of steady use for most popular kits, and although more expensive than strips, they are more accurate. Come as 2-way, 4-way, or deluxe test kits.
- Pool test strips. These are our basic paper strips that you dip into the pool water, wait a determined amount of time, and line up the colors to a key to determine pool chemistry and next steps. Pool test strips are low-cost and generally accurate. There is a degree of eye-balling that happens with strips. Typically available in 4- and 7-way tests.
- Digital pool test kits. For the most accurate results, a digital pool test kit can help you zero in on exactly how your pool water is doing. As you can guess, the increased accuracy comes with a slightly higher price tag, with some of the better models (the LaMotte Color Q is my favorite) costing a couple of hundred dollars. Pool owners that have issues with color blindness will want to lean the way of a digital tester.
In all three cases, testing can be done very quickly, with results showing up in seconds.
3. How often should I be testing the pool?
Regular testing of the pool water is crucial for keeping the water balanced.
Chlorine and pH should be tested at least a couple of times per week. (The CDC, presumably referring to public pools that see a ton of foot traffic, recommends testing twice a day.)
On top of regular testing, there are also other special occasions when you should definitely be testing the pool water:
- When opening and closing the pool
- After heavy rainfall or big storm
- After large groups have used the pool
- When water levels have changed significantly (when adding water or after substantial water loss)
- As part of winterizing your pool
- After seeing visual cues of changes in the water (cloudiness, algae growths, etc)
- Before and after treatment and shocking
New pool owners should test the chlorine and pH 3-5x per week to get a sense of how pool chemicals and chemistry fluctuate based on use and how the elements can affect the water.
Things like calcium, cyanuric acid, and alkalinity are tested less frequently as they take longer to “move” in terms of readings. Depending on the use of your pool, these should be tested weekly, potentially even monthly.
A generalized overview of how often you should test the water:
Chlorine. At least once a week, preferably two or three times. Test both free and total chlorine. Chlorine levels should be within 1-5mm, preferably between 3-5ppm.
pH. Check every couple of days. Look for levels of 7.2-7.8.
Alkalinity. For vinyl or fiberglass swimming pools, an acceptable range is 100-140.
Calcium hardness. Test at least once per month to help prevent your pool water from becoming unbalanced. The target range is 300-500 ppb.
Phosphate. 300-500pb and below. Testing for phosphates–food for algae–is possible but rarely necessary.
Total Dissolved Solids. Aim for less than 1500 ppm. (Not applicable to saltwater pools.)
4. How to take an accurate pool water sample
One of the most important things you have to do when testing the water is collect a sample that is indicative of the overall pool water chemistry.
Commonly, pool owners will kneel and collect water or test the water that is coming out of the return jets/inlets or fresh from the pool skimmer. This water has been freshly treated and cleaned, so it won’t be as representative of the rest of the pool.
Collect water away from the return jets; either at the ends or closer to the middle of the pool.
Additionally, sink the sample collecting container up to your elbow (12 to 18-inches) to avoid collecting water that is sitting at the surface.
5. How to Use a Test Strip
Test strips are the most affordable of the pool testing kits. They are also accurate in a general sense. That said, if peak accuracy is a concern for you, lean towards a digital test kit or a liquid test kit.
Using a test kit is straight-forward:
- Follow the above guidelines for collecting a quality water sample.
- Insert the strip into the container and pull it out. Don’t let the strip sit or soak in the pool water. A quick exposure is sufficient!
- Depending on the brand, hold the strip and let it air dry for around 30 seconds. Avoid the urge to shake it to speed up the process.
- Line up the colors with the attached key or legend.
- Follow the recommendations to balance the pool water.
6. How to use a liquid pool test kit
Liquid test kits are very popular, and my childhood is full of memories of lifeguards using commercial-grade liquid test kits at my early morning swim practices. Using a collector and reagents, you can quickly see what needs to be done to adjust pool chemistry.
- Using the designated collector, pull a quality water sample using the guidelines discussed earlier.
- Add the number of specific drops of phenol red to determine pH values.
- Add the number of specific drops of OTO to determine chlorine levels.
- Close the test vials/collector and invert several times to properly mix the solution with the water.
- Compare colors. To get a good sense of chemical values, hold the collector up against a solid white background (a sheet of paper or stucco wall, for example).
- Generally, the redder the sample, the higher the pH. The same goes with chlorine; a very yellow result signals a high chlorine level.
Once you’ve completed your testing, rinse it out (not in the pool, but with a freshwater source like a sink or the garden hose), dry it out, and along with the reagents (test solutions), store it out of the sun and direct heat.
It’s hard to understate how crucial testing your pool water regularly is. Inground and above-ground swim pools can quickly become hotbeds of bacteria and infectious disease when chemicals are ignored.
With the right testing, not only are we talking about safe water for swimmers, but also the structural integrity of the pool and pool equipment.
And unless we are regularly testing the water, how we are going to know if the water is optimally balanced? Or what kind of nastiness is floating around in it? Or the number of pool chemicals that need to be added to the water?
Testing the pool water is the most frequent maintenance task that has to happen with your swim pool.
This means, that with time, you will get pretty good at it 😉