Last Updated: June 16, 2021

How To Test Swimming Pool Water

Written By: Pool Care Guide

Once in contact with the swimming pool, people’s bodies shed dirt, sweat, oil, sunscreen, sometimes urine and saliva (urgh!), and other stuff which can accumulate and, unfortunately, work against your crystal-clear pool water. Humans aren’t the only threat. These contaminants, and countless others, can lead to many unsavory conditions such as cloudiness, the growth of algae, risks of bacterial infection, etc.

Your most important defense against these contaminants is knowledge, and that comes from testing the chemical balance.  With that knowledge, you can calculate the near-perfect response to any threat, whether it is biological or mineral.

If you wing it or just ignore it, here’s a small list of potential problems you more likely to encounter:

  • Eyes: Infections, red and irritated, and potential permanent vision damage
  • Lungs: Infections, allergies, and asthma
  • Skin: Dry, rashes
  • Pool Equipment: broken from calcium scales, worn down from acidic water
  • Walls: Chalky build-up from calcium scales, acid damage from low pH

When and How Often to Test Your Pool?

The timespan for testing your swimming pool water will depend on how heavily or lightly you use your pool all year round, along with the daily air and pool water temperature. 

Whether you are doing the testing yourself or taking a sample of your pool water to your local pool professional, the testing should be seen as a continuous exercise. To this end, it's essential to test your pool two to three times weekly to maintain sanitizer levels and sufficient water balance and ensure the comfort of swimmers. 

The more pool water testing you do, the healthier your pool water should be. Scheduled testings are recommended. You should also test your chemical balancing in the following circumstances:

  • Before and after unfavorable weather- sweltering weather causes the chemicals to lose their effectiveness as the water evaporates. Additionally, rain is highly acidic and quickly leads to significantly reduced pH levels. This can make it uncomfortable to swim in the pool and can damage pool surfaces and equipment.
  • After adding water to the pool. Tap water pH varies from city to city, but it is often too low. In some cities, “too low” can mean 10x more acid than what is considered healthy.
  • In the summer season- This is when the swimming pool is almost always in use as the season heats up. During this time, your pool’s pH and chlorine levels should be tested at least twice a week at the peak of summer.
  • If the water appears cloudy or discolored
  • After accommodating a large number of swimmers while entertaining poolside

Step-by-Step Process for Accurately Testing Your Pool Water

Gathering a Proper Water Sample

Most pool companies require at least 8 oz of water for pool water testing. Use a water bottle if you do not have the specific sample bottle needed. Empty soda bottles, chemical bottles, or food jars are a definite no-no. Thoroughly rinse out the bottle before you collect each sample. Try to use a plastic bottle as a glass one could break or crack accidentally.

  • Step 1: First, find a location far away from return lines. Take the sample close to the bottom of the pool where the slope to the deep end starts if the pool has both shallow and deep ends.
  • Step 2: Then, immerse the bottle into the water, bottom side, up to about elbow depth (about 18"). 
  • Step 3: Finally, turn the bottle right side up to fill it. When it is full, bring it up to the surface, capping immediately to keep air out.

How to Use Water Testing Kits?

There are kits of three main types: 

  • Liquid Testing Kits
  • Testing Strips
  • Digital Testing Kits

How to Use Liquid Testing Kits?

Liquid test kits are also known as titrimetric pool test kits. They are the most commonly used test kits because they are relatively affordable and have a high level of accuracy. However, most of them are the most difficult to use because they require a sample of pool water, to which the correct number of drops of chemicals is applied to ascertain the balance of chemicals and pH in the pool water.

The kits typically have two to seven dropper bottles included in them, each with a unique reagent to analyze the pool water. 

There are very advanced liquid test kits, but for home use, it is advisable to use pH and chlorine, or phenol red and OTO (Orthotolidine). 

  1. Phenol red is a red chemical added to your pool water sample to check the ph. The redder the water becomes, the higher the ph.
  1. OTO is a yellow liquid chemical that tests for total chlorine. You add it to your pool water sample. The more yellow it turns, the more chlorine there is.

With a liquid test kit, it can be challenging to see the low end of the colors. Ensure you use a white background to examine the colors accurately.

A Few Highly Rated Testing Kits

Amazon offers a wide range of water testing kits. Some of them are highly rated, and some of them aren’t. Many of them only test a couple of the pool chemicals. We want our readers to find the better-rated products that service all of their needs. For this reason, we have compiled a short list to help get you started.

Product NamePriceAmazon RatingsIndexes
Poolmaster Essential Collection$27.224.6 out of 5Chlorine, Bromine, pH, Acid Demand, Total Alkalinity
Taylor K-1000 Basic Residential Kit$13.574.6 out of 5Chlorine, Bromine, Alkalinity, pH, Water Hardness, Cyanuric Acid
HTH 1273 6-Way Test Kit$23.274.4 out of 5Chlorine, Bromine, pH, Alkalinity, Calcium Hardness, Cyanuric Acid
Taylor K-2006 Test Kit$64.004.6 out of 5Acid-Base Demand, Total Alkalinity, amp, Calcium Hardness, FASDPD Bromine
US Pool Supply Premium 5-Way$14.964.4 out of 5pH, Chlorine, Bromine, Alkalinity, Acid Demand

How to Use Testing Strips?

Testing strips are also known as colorimetric pool test kits and are becoming more popular these days. They are easy and quick to use, helping you avoid adding drops of chemicals to several water samples. Anyone can use them. 

A range of testing strips can also test for different ranges and different combinations. If you are on a budget, a testing strip is a way to go, as you can test for 3-6 different ranges with one pack of test strips. 

Using testing strips is very straightforward. Follow these basic steps: 

  1. Dip one strip into the sample pool water and wait for about five seconds. Ensure you have clean and dry hands. 
  1. At the five seconds mark, take the strip out of the water and wait for about 10 seconds for the result to appear. Then you can compare the results against the color chart on the box of the test strips.        
  1. You can go ahead to adjust any of the pool chemicals that need changing as shown on the strip.
  1. Then run a filter pump to help circulate your pool water. Wait for about four to six hours to test the water. If the levels are now in the correct ranges for that particular chemical, no further action is required. But if the above is not the case, you might need to repeat the process all over again.

A Few Highly Rated Testing Kits

Product NamePriceAmazon RatingsIndexes
JNW Direct Pool Test Strips$17.984.5 out of 5Chlorine, Bromine, pH, Water Hardness, Cyanuric Acid
Premium Pool and Spa Test Strips (Varify)$14.974.5 out of 5Chlorine, Bromine, Alkalinity, pH, Water Hardness, Cyanuric Acid
Poolmaster 22211 Smart 4-Way Test Strips$13.184.6 out of 5Chlorine, Bromine, Alkalinity
Pool and Spa Strips (Health Metric Store)$11.974.5 out of 5Chlorine, Bromine, Alkalinity, pH, Water Hardness, Cyanuric Acid
Runbo Pool Test Strips$10.494.4 out of 5Chlorine, Bromine, Alkalinity, pH

How to Use Digital Testing Kits?

Like the testing strips above, these are easy to use and do not need photometers calibrating. They use a set of metallic probes to check your sample pool water and also come with a manufacturer's warranty of two years. They are handy strips and are known for their fast and accurate results in three simple steps:

  1. Get a small amount of your pool water sample in a bottle.
  2. Insert the probes into the fluid.
  3. Read the results on display.

Unfortunately, they also typically cost more than liquid test kits or test strips.

A Few Highly Rated Testing Kits

Solaxx MET20A Safedip 6 in 1$ 218.195 out of 5Free Chlorine, pH, Salinity, TDS, ORP
KodaQo Digital pH Meter$40.994.7 out of 5TDS, pH, Salinity, Electrical Conductivity, Temperature
LaMotte 2056 ColorQ Pro 7$2254.4 out of 5Free Chlorine, Total Chlorine, Bromine, pH, Alkalinity, Calcium Hardness, Cyanuric Acid
Pool Exact EZ Photometer$122.534.1 out of 5Cyanuric Acid, Free Chlorine, Combined Chlorine, Phosphate, Calcium Hardness, Total Chlorine, Chloride, Copper

Testing for the Basics: Ph, Alkalinity, Chlorine, Cyanuric Acid, and Calcium Hardness

Testing your pool water sample for ph, alkalinity, and chlorine almost always go together because they are similar actions. In this section, we shall cover how to test for all of them properly. 

Testing for Alkalinity

Alkalinity is the total alkaline material in your swimming pool water. Testing for it first is advisable as it will buffer pH and affect your ability to change it.  

The pH scale starts at 1.0 and goes up to 14.0. The ideal range for any swimming pool water is between 7.4 and 7.6. Your pool water has a low pH (or your water is acidic) if it is below 7.0 and has a high pH level (your water is alkaline) if it's above 7.0. Sodium carbonate increases your pool pH, while sodium bisulfate decreases it. 

Using test strips for your pool water will test for this. However, if you are using a liquid testing kit, then it becomes slightly complicated. 

For this, you will be using three testing liquids at different times.

  • Carefully read the instructions on your test, and know how many drops of the first two test liquids are necessary, as well as how much water you need.
  • Then add the first test liquid’s drops to the water, Sodium Thiosulfate, and swirl around to combine.
  • Next, add drops of the second, the total alkalinity test liquid, and mix well to combine until the green color is achieved. 
  • Next, add drops of the sulphuric acid, one at a time, duly counting and circling each in until the color becomes red.
  • Use the sulphuric acid drops, 10 times, to determine the total alkalinity. Eight drops mean an 80 total alkalinity which is low, and ten drops (100) are high.
  • Consequently, take action to increase or reduce your pool's alkalinity if necessary.

Testing for pH, Cyanuric Acid, Calcium Hardness, and Chlorine

Having already addressed the significance of testing for pH and chlorine in your swimming pool, we will now move on to calcium hardness and cyanuric acid. 

Calcium hardness is the measure of how hard or soft your swimming pool water is. It measures the amount of dissolved calcium and magnesium in your swimming pool. 

The hardness of water is an integral part of the water balance calculation, along with pH, alkalinity, and sometimes the temperature.

Commonly referred to as a chlorine stabilizer, Cyanuric acid is often used in outdoor pools and spas to stabilize chlorine levels. Without cyanuric acid present, chlorine can quickly be degraded by UV light. Levels of Cyanuric acid should be tested weekly with photometers which are a well-known test method.

Testing for Copper

Copper and iron in your swimming pool water enter when metal objects fall into it. Metal objects like poles, toys, tools, etc., can damage or discolor your swimming pool surface and corrode metal elements in direct contact with your pool water. 

Test your swimming pool water for copper by using copper test strips. Dip the test strip into the pool water for about five seconds. Remove the strip and shake once. Wait for about 15 seconds, then compare the color on the strip with the color chart which comes with the kit to determine if copper is there in your pool water or not. 

Ideally, the level of copper should be zero. This is only a general guide, though. Do follow the instructions on your purchase and test the water sample accordingly.

Note- We advise testing pool water for copper once a month. Also, you will need to do a copper test if your pool water has a low pH level. 

Testing for Iron

Too much iron in your pool water can have crushing effects on your pool, impacting hair and nails. So, it goes without saying that it's essential to be aware of the signs of excessive iron before it leads to rusting in your pool.

You can test your pool water with an iron test kit to determine if iron is indeed the culprit of the problem in your pool. 0.2 parts per million (PPM) of iron is sufficient to cause staining and clouding. If you prefer, you can take a sample of your pool water to your local pool supply store for iron testing.

Note- We advise you to test your pool water for iron once a month. And test again if you notice a brown coloration or have a low pH reading.

Testing for Calcium

This is exactly similar to testing for calcium hardness or water hardness.

Schedule for Testing Pool Water for Calcium- Once every month

Testing for Phosphates and Nitrates

Phosphates alone aren't a pool water quality problem. So most pool kits do not include phosphate level tests. Algae is the problem, and most pool owners already have one method or the other to control algae.

Schedule for Testing Pool Water for Phosphates- It is unnecessary. But if you want to, go right ahead. 

Testing for Salt

Unless your pool is a saltwater pool, you do not have to test for salt levels. 

Not maintaining the minimum salt concentration needed for your saltwater swimming pool can cause your salt chlorine generator to produce insufficient amounts of chlorine. This can lead to algae and bacteria growth. Also, adding excessive amounts of salt to your swimming pool increases your chemical expenses. Salt test kits can be found in the form of liquid and strips. And you probably have an algae problem if your salt-water pool is turning green.

Note- Salt levels should be tested monthly. You should also test immediately if any of the following occurs – you add water to the swimming pool; there was a rainstorm or excessive use of the swimming pool.

We hope that reading this article has helped you gain more confidence in your pool water testing and enabled you to enjoy healthy, balanced pool water this summer and many more in the future.

Common Questions About Pool Water Testing

What Is the Most Accurate Way to Test Pool Water?

If you want accuracy and consistency, digital test kits are the way to go. Liquid test kits are also extremely precise. However, there is a lot of room for human error because a single extra drop of testing fluid will throw off the readings.

What Order Should I Adjust My Pool Chemicals?

There is a delicate balance between all of your pool chemicals. When you add one, it affects all of the others. When we adjust our pool chemical balance, our first priority is to achieve a neutral saturation index. 

The saturation index is how we classify a pool’s placement on the scale between water that is corrosive and water that is basic and prone to calcium scaling. We need to bring this saturation index to a neutral point. After that, we can add our sanitizer. To accomplish all of that, add your pool chemicals in the following order.

1. Total alkalinity
2. pH
3. Calcium hardness
4. Sanitizer

What If You Put Too Much Chlorine in Your Pool?

First, if there is too much chlorine, you should stay out of it. Second, this problem fixes itself. Chlorine naturally and quickly evaporates unless it has a chlorine stabilizer to keep it in the pool. If you have overwhelmed the stabilizer with chlorine, leave the pool alone for 24 hours and retest it.

If you need a faster solution, there are ways to actively neutralize chlorine. Chlorine cleans your pool by binding to hydrogen atoms. When it binds to them, the chlorine is neutralized. Hydrogen peroxide is a safe, effective, and accessible way to add these hydrogens to your pool.

Alternatively, sodium thiosulfate and other chlorine neutralizing products are available at most pool stores.

Can You Reuse Test Strips?

Unfortunately, you cannot reuse test strips. The chemicals on these strips will not revert to a pre-tested state. Testing with the strips again would provide inconclusive and ultimately useless results.

How to Test Pool Water for Electricity

Some digital water testing kits can test for the electrical conductivity of water. However,  if you want to test for electricity in the water, you will need to purchase a voltmeter.

How Much Does It Cost to Get Pool Water Tested?

Generally speaking, most pool services do not offer the singled-out option of testing pool water. It usually requires hiring a pool service package. Fortunately, these packages are generally set in an affordable price range between $30 and $90.

Do Swimming Pool Test Strips Go Bad?

Yes, pool strips do go bad. Pool strips generally last between 2 and 3 years.

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