How Often Should I Test My Pool Water?
This is a common enough question. And, like so many questions involving pool water maintenance, the answer is, “it depends.”
That’s not to say there’s no rule of thumb you can go by. If that’s all you’re looking for, we recommend you test your pool water at least weekly — but ideally, 2 to 3 times per week. Some pools under some conditions, though, may need to test even more often.
Why testing pool water is important
Regular pool testing is a critical part of maintaining proper chemical balance. As you probably already know, your swimming pool wouldn’t be all that great to swim in if it was filled with nothing but tap water. Since swimming pool water isn’t constantly being replenished like a natural spring, it would very quickly turn into a swamp without the proper mixture of pool chemicals to keep it clear and sanitary.
The main factors you need to be concerned with are:
- pH level - A measure of how acidic or basic your pool water is, based on the pH scale which runs from 0 to 14, with 7 being neutral (like pure water). The optimal pH level for your pool is around 7.4, or just slightly more basic than regular water. Any lower than that and the pool water can become corrosive, damaging the liner, fittings, and accessories. Much higher than that and it starts inhibiting what your chlorine can do.
- Alkalinity - A measure of the hydroxides, carbonates, and alkaline substances in the water. At the right level, these substances help keep your pH level more stable. You’re looking for a level somewhere between 80 and 120 ppm. If your total alkalinity gets too low, you’ll find it nearly impossible to maintain the right pH.
- Chlorine level - You know your pool water needs chlorine to keep it clean. But, it’s a delicate balance. Too little chlorine and you risk algae and bacteria buildup. Too much, and it’s not a pleasant swimming experience. When testing for chlorine, you’ll need to cover two figures: free chlorine, which is the amount of chlorine still available to clean the water, and total chlorine, which includes all the chlorine that’s been “combined” with contaminants and is no longer useful. The optimal level of free chlorine is 1 ppm, and if your combined chlorine (total chlorine - free chlorine) goes any higher than 0.3 ppm, you’ll need to “shock” the remove all those contaminants.
- Cyanuric acid level - This substance serves as a stabilizer to prevent sunlight from breaking down the chlorine too quickly. Without it, you’ll find it impossible to keep your chlorine levels balanced, and you’ll be spending a fortune on chlorine. An optimal CA level is between 30 and 50 ppm.
A balanced pool is fresh, clean, and comfortable. It looks clear and inviting, smells pleasant, and feels great on the skin. On the other hand, pool water that’s out of balance can be cloudy, discolored, and smell bad. Even worse, it can be irritating to the skin and eyes, and can even make you sick.
How and when to do your pool water testing
Using a pool test kit regularly helps you make sure your water stays in that “sweet spot” where all the various pool chemicals are optimally balanced. When you test often, you can make small changes to the chemistry to keep the water clear and healthy. That way, you’ll spend less money and use fewer chemicals.
We also highly recommend testing anytime there’s a significant change to your pool water. This would involve anything that changes the volume of water in the pool or introduces more than the average contaminants. Some examples include:
- Heavy or lengthy rains
- Unusually hot weather
- Fertilizer, grass or leaves blow into the water
- Heavy usage of the pool (i.e. hosted a party)
As noted in our introduction, testing 2-3 times per week is usually sufficient to keep everything in balance barring unusual events like the ones listed above. Under difficult circumstances, you may need to test your pool water multiple times a day for a while until you have it under control.
A quality pool water test kit is essential.
The most useful type is one that tests for pH, chlorine, total alkalinity, hardness, and cyanuric acid levels, all at the same time. You can use either test strips or test solutions, though we recommend test strips for better reliability and longer shelf life.
If you choose to use test solutions, remember that they have a limited shelf life and lose their accuracy if exposed to sunlight and heat. Store them in a cool, dry area.