Pool Water Testing

The two most popular ways of testing pool chemicals are pool test strips and pool testing kits. Whether you use a kit or a strip, it should measure chlorine and pH levels. These measurements show two of your pool’s most important chemical readings.

It’s best to find a kit or strips that also measure total alkalinity and total hardness. Total alkalinity can negatively affect your water’s pH. Unbalanced total hardness can cause damage to pool surfaces and equipment.

As you conduct pool water testing, track the chemical levels. Use a journal or logbook to write down the data from each weekly test.

Pool test strips are a fast and convenient pool water testing option for measuring total hardness, total chlorine, free available chlorine, pH, total alkalinity and stability. Many pool owners find test strips are economical and simple to use. Strips are also easy to read.

How to test pool water with a strip:

• With clean, dry hands, remove one test strip from bottle. Close the bottle tightly.
• Dip the test strip into your pool at elbow depth and away from jets for 15 seconds.
• Remove the test strip from the water.
• Compare its results to the chart provided in the package.

Tip: The test strip container may provide general guidelines on balancing chemical levels.

The two popular types of test kits are DPD tests and OTO-Phenol tests. DPD tests usually measure chlorine, pH, alkalinity, stabilizer and hardness. OTO-Phenol kits test for chlorine and pH. Pool test kits can be more time-consuming than test strips. However, they are typically more accurate.

How to use a pool test kit:

• Remove the tube caps. Rinse tubes before use.
• Fill the tube with pool water up to the indicator lines. Make sure to take your sample in an area at elbow depth and away from the jets.
• Once a tube is full of pool water, follow the directions on the package. Drop the appropriate amount of the reagent solution into the water sample.
• Cap the tube and shake gently to thoroughly mix the solution.
• Compare the color of the water in the tube to the chart provided in the test kit.

For balanced pool water levels, here’s what you need to measure and often you should do the tests:

Free Chlorine

• Helps prevent the growth of bacteria and algae.
• Test 2 to 3 times a week.
• Ideal range: 1 to 4 parts per million (ppm).

pH

• Helps prevent swimmer discomfort, improves chlorine effectiveness and protects equipment.
• Test 2 to 3 times a week.
• Ideal range: 7.2 to 7.6.
• When a pool's pH falls outside the acceptable range, you may need to use pH adjuster.

Total Alkalinity

• Helps prevent pH from swinging in and out of range.
• Test weekly.
• Ideal range: 80 to 150 ppm.

Calcium Hardness

• Helps prevent surface damage such as scale and corrosion.
• Test monthly.
• Ideal range: 175 to 275 ppm.

Stabilizer

• Stablizer extends the life of chlorine by preventing chlorine burn-off due to sunlight.
• Test 2 to 3 times per season.
• Ideal Range: 30 to150 ppm.

If you have a saltwater pool, you still need to do pool water testing each week. The correct balances of free chlorine, pH, alkalinity, calcium hardness and stability should be the same as for a traditional chlorinated pool. The schedule for testing each chemical is the same, too. Saltwater pool testing should also include measuring salt levels each month.

The chlorinator in your saltwater pool probably shows a salt reading. Still, you should perform your own salt tests to see if the chlorinator’s readings need to be corrected. You can use a test kit or test strips made for saltwater pools.

• The salt level in your saltwater pool should be between 2,700 to 3,400 ppm.
• An ideal measurement for salt is 3,200 ppm.
• If your salt measurement is low, you may need to add salt to your pool.

You may need to test your pool water more often depending on how much you swim, who uses the pool and what the weather is like. When you’re going for a dip or swimming laps more than once a day, measure the free chlorine four to five times each week.

If pets or little kids use your pool, you should also be testing the free chlorine four or five times each week. Pets and kids are more likely to go to the bathroom in the pool, which affects the chemical levels greatly.

Having a pool party? Test the pool water before your guests arrive and after they leave. The more people who use the pool, the more the chemical balance will be affected. Taking measurements prior to the party and afterward will help you see exactly how the numbers change.

When it rains, a lot of fresh water can end up in your pool, which can make the water more acidic. After a storm passes, test your pool water’s free chlorine and pH as soon as possible.