What should you test in swimming pools?

Accurately measuring the key parameters in your swimming pool is a fast and easy way to maintain good health and safety standards and keep your water in optimum condition. The first step to testing with a suitable digital tester for pools is knowing which parameters are the most important and the ideal range that your water levels should be within to make it safe for swimmers. We cover some of the most important tests for pool water below:

What should you test in your pool?

The key parameters for swimming pools can vary depending on a few factors, such as if the pool is outdoors and the volume of bathers. Businesses that operate pools, for example, will have more stringent health and safety requirements than private swimming pools. However, it’s important to use the best testing methods available, like digital testers, to measure at least the most important parameters in any pool to ensure the water is safe for use.

The parameters you should test in your pool water include:

• pH
• Chlorine
• Cyanuric Acid
• Conductivity
• TDS
• Total Alkalinity
• Calcium Hardness

Of all the parameters on this list, pH and chlorine are the strongest requirements for maintaining a healthy pool. Sanitation is vital for making the water safe for bathers, while pH influences the effectiveness of chlorine and affects all other parameters as well. 

To learn more about the best testers to measure pool water, see our complete guide here.

pH

For all pools

pH is a scale from 0 to 14 and measures how acidic or alkaline the water in a pool is. 7 pH is the central, neutral point for this parameter, with anything above 7 being more alkaline and everything below 7 being more acidic. pH increases in strength 10x per unit, which means a pH of 6 is 10x more acidic than a pH of 7.

For most pools, the ideal range for pH is between 7.2 and 7.6. This slight alkalinity provides the best conditions for sanitation, ensuring the pool is safe for use. It’s important to measure pH at the correct temperature, as the temperature of your water affects the pH level.

An electronic digital tester is an easy and reliable way to test the pH in pools. These electronic meters can be dipped directly in the water to achieve an accurate measurement. You could also opt for an automatic controller system where the pH and chlorine in the water are measured and dosed with no intervention required.

Learn more about pH testing for pools in our article here.

Chlorine

For all pools

As the most common pool sanitiser, chlorine is an extremely efficient way to keep pool water safe for bathers and free of pathogens. This chemical’s effectiveness is influenced by pH levels, making pH testing an important first step before you measure chlorine in pool water.

Free chlorine is the ‘active’ part of chlorine that works to disinfect the water. The ideal range of free chlorine in swimming pools varies based on the size of the pool, the frequency or use and the number of swimmers using the pool. To give a general idea, around 0.5 to 1.5mg/L is a good range for indoor pools, with a range of 0.5mg/L to 3mg/L being suitable for outdoor pools.

A digital photometer is a reliable and accurate way to monitor the chlorine within swimming pools. Or, if you prefer a hands-free approach, you can opt for an automatic pool controller that measures and doses pH and chlorine.

Cyanuric Acid

For outdoor pools

Cyanuric acid is a common additive to outdoor pools as a method to protect chlorine from degradation caused by UV rays. While a certain level of cyanuric acid is required to prevent this degradation, too much can cause chlorine to become too stable and less effective as a sanitiser as a result. A telltale sign of high cyanuric acid is the presence of algae blooms in water where chlorine is at a correct level.

Keeping cyanuric acid under 70 mg/l can ensure sanitation is as effective as possible. Stabilised chlorine typically includes this chemical, making it an important parameter to measure if you utilise these kinds of tablets or powder. Monitoring cyanuric acid helps to prevent it from reaching the maximum effective range for sanitation, preventing the need to drain the pool.

An electronic photometer is an easy and precise way to measure the amount of cyanuric acid in outdoor pools. A multiparameter meter covers all of the most important pool parameters in one for peace of mind in pool care.

Total Dissolved Solids

For all pools

Total Dissolved Solids, or TDS, is a key measurement in pools that have a high volume of bathers. This parameter measures the total ions in a solution, the dissolved compounds found within the water that typically occur over time with a large number of swimmers. Public pools, gyms, holiday parks and leisure centres may want to measure TDS.

Ideally, TDS should be no more than 1000 mg/l higher than the incoming fill water. Measuring this parameter is a simple task with a dip-and-test TDS tester for pools, allowing you to easily test pool water directly in different locations.

Total Alkalinity

For all pools

Alkalinity acts as a buffer in the water against significant changes in pH, effectively working to stabilise the pH level without large swings that require dosing or emergency remediation. Alkalinity particularly helps to prevent overly significant changes from pH-changing chemicals introduced to the water, allowing dosing to be more precise.

A typical ideal range for total alkalinity is 80 to 120mg/L CaCO3 (calcium carbonate). A multiparameter photometer is a reliable option for measuring alkalinity in pools alongside a range of other vital tests to keep pool water healthy.

Calcium Hardness

For all pools

Also known as total hardness, calcium hardness is a useful measurement to preserve the lifespan of your pool. Over time, calcium hardness causes scaling in the pool that can encompass a range of essential fixtures, such as heaters, pumps, jets and pipework. If there is too little calcium in the water, corrosion can occur as metal parts have less protection. Cloudy water can be an indicator that calcium hardness is high.

A typical range of total hardness is 80 to 200 mg/l CaCO3. A small digital Checker is an accurate and simple way to monitor calcium hardness in pools, requiring only a small water sample and single-button operation to get clear, electronic results.

Other parameters to consider for pool testing

Alongside the parameters listed above, there are other tests for swimming pools you may want to consider. 

• Nitrate and phosphate: These compounds can build up and cause eutrophication, particularly in outdoor pools, which may lead to rapid algae growth regardless of the sanitation in your pool.
• Turbidity: This parameter measures how cloudy the water in the pool is and may indicate issues with the pool chemistry or the filtration system.

What parameters are important for hot tubs?

All of the parameters that are important for pools also apply to hot tubs, though the recommended ranges may differ. pH and chlorine testing is as important in hot tubs and spas as it is in swimming pools for the health and safety of bathers. To learn more about testing the water in hot tubs, see our article here.

Are digital testers the best option for testing pool water?

Choosing digital testers or photometers is a precise and easy way to measure all of the important parameters in swimming pools. Unlike strip tests for pools or swimming pool test kits, an electronic meter provides accurate and clear measurement results on a screen. This allows you to make changes to your water chemistry quickly and effectively, with none of the guesswork of reading colour charts. Learn more about digital pool testing here.

Shop digital equipment for pools today

Buy electronic testers for pools, digital photometers and completely automated pool controller systems from Hanna Instruments today. Our comprehensive range of Pool Line instruments makes pool testing easy. Browse the range online now.

Have questions for the specialists? Contact our expert pool ambassadors today at 01525 850 855 or at sales@hannainstruments.co.uk to discuss your requirements.