Pool testing is the most critical part of pool maintenance. Ideally, testing should be done weekly at a minimum.
However, external circumstances may force you to test more often. Heavy rains or extra bather loads will require additional testing to ensure water levels are still balanced.
Some chemical levels require more attention than others. Let’s take a deeper dive into what should be tested and some basic tips.
When Should I Test More Often?
Typically, when the pool is being used frequently, testing should be done more often. More use can alter the overall water balance and may need extra attention to add more chlorine.
Nature can also warrant additional testing. Heavy rains can dilute some of the chemistry levels. Conversely, consecutive days of hot and dry weather can eat up chlorine levels faster than normal, leading to algae blooms.
Lastly, new and resurfaced plaster pools need extra attention in the beginning. As the plaster cures, the pH will significantly rise. You may need to test the pH two to three times a day for the first month until it gets under control.
Your pool has a personality! Until you have a good grasp on how the water reacts on a weekly basis, more frequent testing should be done.
What To Test For and Testing Cadence
No matter what type of pool you have, the chemical levels that are being tested remain the same. There is the exception of an added test for salt with a saltwater pool, but all other tests are identical. Any viable testing kit should be able to test all of these parameters:
- Free Chlorine (FC): FC measures how much chlorine, or another sanitizer of choice, is in the water. It tells us the amount of chlorine that is available, or “free”, to fight algae and other living contaminants. Because of its importance, FC should be tested daily or at least every other day.
- Combined Chlorine (CC): While FC looks at chlorine that is available to fight, CC measures any current reactions with algae or living organisms that it is attacking. Since it is typically an additional test to FC, CC should be tested when FC gets tested.
- Cyanuric Acid (CYA): CYA is chlorine’s stabilizer. It helps block the sun’s UV rays from degrading FC too quickly. If CYA gets too high, more chlorine will need to be added. Conversely, little to no CYA will force you to add more chlorine as the sun burns through it more quickly. Depending on what type of chlorine is used, CYA can be tested on a weekly or monthly basis. Using trichlor tablets will raise CYA over time so additional testing may be necessary to ensure it is not out of balance.
- pH: pH measures how acidic or basic the pool water is. Because it tends to drift up over time naturally, pH should be measured weekly.
- Total Alkalinity (TA): TA acts as pH’s buffer. It is there to stabilize pH as much as possible. Ideally, TA is measured weekly along with pH.
- Calcium Hardness (CH): CH tells us how much calcium is in the water. This is usually more important for owners of plaster and gunite pools. Since CH doesn’t tend to change too much unless calcium is added, CH can be tested weekly.
- Salt (for owners of a saltwater pool): This test will measure how much salt is in your pool. To make sure the pool has the correct amount, salt should be tested at least once a week
| Chemistry | Cadence |
|---|---|
| Free Chlorine (FC) | Daily |
| Combined Chlorine (CC) | Daily |
| Cyanuric Acid (CYA) | Once a week |
| pH* | Once a week |
| Total Alkalinity (TA) | Once a week |
| Calcium Hardness (CH) | Once a week |
| Salt | Once a week |
Know Your Pool
Only you know how often the pool should be tested. Testing is a learning process. It may make sense to test more often than needed until you have a better grasp of how water fluctuates week to week. Once you get it down, which you will, pool maintenance will be that much easier.