How to read a pool test strip - Sutro, Inc

How to read a pool test strip

Maintaining the optimal levels of water chemistry in a pool is essential for proper maintenance, eliminating potential safety or health hazards, and informed use of chemical treatments.

The most widespread method of doing this is to use a pool test strip (which we’ll be learning about here). 

By the end of this short guide, we will introduce you to an innovative alternative to these ineffective test strips. Let’s dive into it.

Why should you use pool test strips? 

Pool test strips are the simplest and cheapest method for measuring the water chemistry of a pool.

Although there are many factors to measure, the most critical tests are for pH and chlorine levels

The readings from a strip help you understand various factors for pool maintenance, like when to use pH up or pH down and when to raise or lower the total alkalinity levels in your pool or spa water.

For example, if you shock your pool and do not measure the pH and alkalinity levels soon after, it may result in a pH imbalance which can cause serious problems such as scaling or cloudy pool water.  

There are three different types of strips available on the market, which differ in the number of parameters they measure.

There are 5-in-1 strips, 6-in-1 strips, and 7-in-1 strips, also known as five-way, six-way, or seven-way strips.

Additionally, the most common brands for pool strips in the North American market are Clorox®, Pool&Spa™, and Multi-Use Smart Strips™.

These are the primary markers of pool chemistry measured by a pool test strip:

  • Total alkalinity
  • pH levels
  • Free chlorine 
  • Calcium hardness
  • Cyanuric acid (stabilizer)
  • Total chlorine
  • Total bromine

Each of these markers has significance in maintaining optimal pool water chemistry, which we will cover in detail in the upcoming sections. 

How to use a pool test strip? Step-by-step  

Using a test strip in your pool is simple and quick. Just follow this step-by-step guide.

  1. Ensure the pool pump runs for at least an hour before commencing the test. This will ensure that the water is mixed, and you will get the most accurate readings.
  2. Pull out a single strip from the packet, hold it from the blank end, and dip it into the pool or spa water at the elbow’s length of your arm.
  1. Keep it submerged in the water for 3-4 seconds, then pull it out.
  2. Do not shake or wipe the strip to remove excess water because it may prevent the pads from reacting correctly.
  3. Wait 15-30 seconds for the colors to settle.
  4. Match the corresponding colors on the strip to the table on the box/packet of strips and discard it afterward. Never reuse strips. 

How to Read Pool Test Strip Results (Color Chart)

Now that you are familiar with using a pool test strip let us understand what each color and number on the pool strip means.

Before you begin, refer to the color chart on your box/packet of pool strips to understand each marker's position and color values on your test strip.

The graph will also outline the good, bad, and optimal values for these markers. 

  • Total Chlorine: This is the total amount of chlorine present in your pool water, and it should optimally lie in the range of 1-4 ppm (parts per million).

    A lesser value will call for the shocking of your pool, and a higher value will require the application of chlorine reduction methods.

    You must also remember that chlorine levels will reach 5-10 ppm levels after a pool shock, so you must wait for at least 24 hours before conducting a test. 
  • Free Chlorine: This is the amount of unused chlorine in the pool water which can still kill bacteria and microorganisms in your pool. Its ideal level is between 2-4 ppm. 
  • pH Level: the pH level of pool water measures its acidity. The optimal value for this lies between 7.2 to 7.8 on a scale of 1 to 14. 
  • Total Alkalinity: It is closely related to pH levels and refers to the ability of pool water to resist a change in pH. The optimal range for total alkalinity in a pool is between 80-120 ppm. 
  • Cyanuric Acid: It is also called a stabilizer because it maintains the chlorine levels in your pool water, as they can fall quickly under direct sunlight and other factors.
    The ideal level of Cyanuric acid is between about 30 ppm and 60 ppm for pools in direct sunlight. 
  • Calcium Hardness: Also known as total hardness, this measures the total amount of dissolved minerals and calcium in your pool water.

    Maintain a reading between 175 – 275 ppm. Failing to do so will significantly damage your pool equipment and can contribute to scaling and white lines on the tile.
  • Total Bromine: The ideal range is between 3-5 ppm. A higher concentration will result in skin and respiratory issues for the users. 

What kind of test strips do I need for a small pool?

The pool size is not a deciding factor in choosing pool test strips. That’s because the strip measures the overall levels of different markers in the water by utilizing a small sample.

However, the only essential requirement is that the pool water is properly circulated/mixed to determine an accurate value of the markers.  

What else can you use to test the pool? 

Other than the pool test strips, liquid-based pool testing kits can be used for evaluating water chemistry. It is like a small laboratory-in-a-box setup, where you take a sample of your pool water and mix it with different chemicals in the kit to measure your chemistry.

Another option is to take a sample of your pool water to a pool store for evaluation.  

How often should I test pool water?

The exact frequency for testing your pool water will depend upon usage, environmental factors, and maintenance activities.

For example, you must consider testing pool water after shock, heavy use, rain, a change of water, use by pets, or after adding any chemicals. 

The frequency can range from 2-3 times a week for pH and chlorine checks to once a month for total hardness and stabilizer levels. 

Can you use a pool test strip for a hot tub?

Yes, you can use a pool test strip for a hot tub. However, you will have to be aware of the sanitization method used for the water.

Some hot tubs use bromine-based sanitizers (instead of chlorine-based), so you must use a seven-way pool test strip to test for bromine.  

Forget about manual testing. Sutro is the automated way.

Keeping track of the pool water chemistry can be time-consuming. What if we told you that instead of using pool strips or test kits every couple of days, you could automate the process with a water monitor?

Our Sutro Water Monitoring System for Pools and Hot tub is a water monitoring device that measures your pool chemistry. You don’t need kits, strips, or tables.

Sutro sends results and recommendations directly to your phone, so you can track your water chemistry without lifting a finger.

Back to blog