Pool care basics – water testing and balancing

Want a great looking pool but don't want to spend all your time looking after it?

The quick answer

It's important to keep your pool clean and sanitized — check out my last post for more information on that.

Testing and balancing your pool water should be done weekly or as needed after events like heavy use or windstorms. The main components you'll be testing for and then balancing are sanitizer (chlorine or bromine), total alkalinity and pH.

New pool owners are encouraged to have their water tested regularly by a pool professional. Most pool companies provide this as a free service.

Still here? Great! Read on to learn more about testing and balancing your pool water.

Before we test the pool water it's important to know why we need to test and balance. Properly testing and balancing your pool water keeps your swimmers safe and protects your investment. It is essential for proper disinfection and overall water quality and also helps preserve your pool surfaces and equipment.

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Water testing

Testing your pool water tells you what chemicals you need to add to properly balance it.


Take your water sample in a location away from return lines and dead zones, like corners or steps. If your pool has a shallow and deep end, take the sample near the point where the bottom of the pool starts to slope down. If the water is of uniform depth, positioning is not as important. If you're testing a spa, make sure the jets and blowers are turned off. How deep should you go? Aim to sample 12 to 18 inches below the surface.

When adding drops of any reagent to a water sample, hold the reagent bottle vertically. Holding the bottle at an angle may distort the drop size and lead to inaccurate results. Swirl the sample around to mix thoroughly. Proper results will depend on colour comparison or a colour change. Pro tip: when matching your colours, be sure to have your back to the sun. Facing the sun will give you too much light to get an accurate reading.

Remember to keep your test kit clean, tighten caps on reagents between tests, rinse out the sample comparator between tests, avoid leaving the kit in direct sunlight and protect it from freezing during the winter months.

So what should you test your pool water for?
  • Sanitizer: Disinfectants such as chlorine or bromine keep the water sanitized. They react with and kill micro-organisms and oxidize contaminants to protect swimmers from impurities brought into the water by the environment or other swimmers. The ideal level for chlorine is 1 to 3 ppm and the ideal level for bromine is 2 to 4 ppm.
  • Total alkalinity: Total alkalinity is tied to pH (see below) and should always be balanced before pH. Total alkalinity is the key to water balance. It's the measurement of the water's ability to resist changes in pH. It's also known as the buffering capacity of water. High alkalinity makes it hard to change pH and contributes to scaling and cloudy water. Low alkalinity causes dramatic changes in pH known as "pH bounce" and leads to pool surface and equipment corrosion. The ideal total alkalinity range is between 100 to 120 ppm.
  • pH: Testing for pH will tell you the relative acidity of your water. High pH readings indicate an alkaline pool that can promote scale formation and cloudy water. Low pH readings indicate an acid pool that can increase pool surface and equipment corrosion, as well as skin and eye irritation. Both high and low pH can reduce the effectiveness of sanitizers. The ideal pH range is 7.4 to 7.6 for pools and 7.2 to 7.8 for spas.
Other tests:

Calcium hardness and total dissolved solids are both important factors in pool and spa maintenance, but pool owners do not typically do these tests. It’s best to take a water sample to your pool dealer. Most do not charge for this service.

  • Calcium hardness: Calcium hardness indicates the amount of dissolved calcium in your water. Often overlooked because it doesn't affect bather comfort, it can have a major impact on your pool surfaces and equipment. High calcium hardness is characterized by cloudy water, scaling on pool surfaces and reduced filter effectiveness as the filter sand calcifies. Low calcium hardness indicates aggressive water, which can pit concrete, cause staining and make liners brittle. The ideal range of calcium hardness for a concrete pool is 225 to 275 ppm and for a vinyl pool is 150 to 275 ppm.
  • Total dissolved solids (TDS): TDS is a measurement of the minerals, chemical residues and other particles in your water. As your pool water evaporates, these solids stay in your pool. This matter accumulates over time and acts as a sponge, consuming your chemicals, and rendering them virtually ineffective. Water with a high TDS reading can be corrosive. There are a few indicators that may tell you that your TDS reading is too high. One indicator is the continual addition of excess chemicals. Or your water chemistry tests may be fine, but the water is still not clean, clear, blue and sparkling. Or you may have algae growth despite a good chlorine reading and proper water chemistry.
Water balancing



Got it? Okay then. Your testing results will tell you which chemicals you need to properly balance your pool water. Adding pool chemicals is the final step.

Before starting, know the volume of water you are balancing so you can add the right amount of chemicals to it.

There are many chemicals involved in pool care. Here's an overview of the major chemical groups:

  • Sanitizers: Sanitizers include chlorine and bromine (salt water pools use chlorine generated from salt). Sanitizers come in different forms including stick, puck, granular or liquid. Each form offers different advantages and disadvantages in terms of cost and effectiveness.
  • Balancing chemicals: Balancing chemicals are used to adjust total alkalinity, pH and calcium hardness (calcium hardness can be raised with chemicals, but only lowered with dilution).
  • Oxidizers: Oxidizers are in the same category as sanitizers and are commonly referred to as shock. You will need to use these weekly to keep your water safe and to maintain your pool surfaces and equipment.
  • Specialty chemicals: Specialty chemicals include different types of algaecides. When used weekly, these can kill algae and prevent algae build up even if your sanitizer level gets too low. There are also a large assortment of products for stain and scale prevention, water enhancing, and tile and cover cleaning.

Confused? Knowing what product to use can be a little overwhelming at first, but in time you'll get to know the products and when to use them. In this industry there is always something new to learn, as problems differ from pool to pool, and each body of water has its own unique qualities.

Want even more information on pool care? Feel free to get in touch.

Surfing the Internet is a good start. But your single most important step for pool information is to contact a certified pool professional to make sure you get the custom advice you need.

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Brian Lilleberg
Betz Pools

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