What Do Pool Chemicals Actually Do?

Keeping your pool clean and clear involves more than simply adding chlorine. In this article, we’ll explore how some of the most common pool chemicals actually contribute to clean, balanced pool water.

Sanitizers

Sanitizing chemicals are designed to kill bacteria and other microorganisms, helping keep your pool water clean, clear and safe to use. Simply put, without a sanitizer (most commonly chlorine) bacteria and other contaminants would quickly begin to multiply, leading to cloudy water and potentially unsafe swimming conditions.

Sanitizing chemicals come in a few different forms; most commonly:

Tablets

Sanitizing tablets (also called “pucks” or “sticks”) are chlorine that has been compressed into a larger, solid form. They are designed to dissolve slowly, releasing chlorine into the pool over several days.

Because tablets dissolve gradually, they are used to maintain a consistent level of sanitizer in the water over time. They are typically placed in a floating dispenser, skimmer or automatic chlorinator, depending on the pool system and the type of tablet being used.

Shock Treatments

“Shocking” a pool is the process of adding a high dose of an oxidizing chemical to the water. Shock treatments help break down organic contaminants that build up in the water over time such as sweat, oils and sunscreen.

Regular shocking gives your sanitizer a helping hand by breaking down contaminants that can consume chlorine and make it less effective. How often you need to shock your pool depends on factors such as pool usage, weather and water conditions; but is most commonly done once per week.

Stabilizer

While not a sanitizer itself, pool stabilizer (also known as cyanuric acid or CYA) helps protect chlorine from being broken down by the sun’s ultraviolet (UV) rays. Without stabilizer, sunlight can quickly reduce the amount of available chlorine in an outdoor pool, meaning you may need to add sanitizer much more frequently.

Together, sanitizer, shock and stabilizer play important but different roles. Chlorine provides ongoing sanitation, shock helps deal with contaminants, and stabilizer helps protect chlorine from UV radiation. Keeping all three properly managed is an important part of maintaining clean, clear and healthy pool water.

Balancing Chemicals

Water “balance” is the relationship between different chemical measurements in your pool water. It is based around how water reacts when other particles are introduced to it.

Essentially, water dissolves and holds minerals until it becomes saturated and cannot hold any more. This is known as the water’s “saturation point”. When the water balance dips below the saturation point, it becomes corrosive. Water that is corrosive will try to saturate itself by dissolving everything it comes in contact with. When water is above the saturation point, it becomes scale forming. It can no longer hold all of the minerals that are dissolved in it. The excess minerals will then “fall out of solution”, grouping together and forming scale on any surfaces within the water.

The goal of balancing chemicals is to keep your water as close to the saturation point as possible. Each one is designed to do one of 4 things:

• Increase Alkalinity
• Increase pH
• Decrease pH or Alkalinity
• Increase Calcium Hardness

pH Increasers

pH is the measurement of how acidic or basic the water is. Pool water with a low pH (below 7.2) is considered acidic. Over time, acidic water will break down key components of your pool equipment, especially metal components like the heater element and rubber components like gaskets and seals. It will also cause the water to feel more “harsh” when you use the pool and can cause your eyes to get red and irritated.

Alkalinity Increasers

Alkalinity is essentially a “buffer” for pH. The lower the alkalinity of the water, the faster its pH levels will change. Almost everything you add to the water (including yourself) has the potential to change the pH of your pool water. Low alkalinity therefore makes it very difficult to maintain an acceptable pH level in your pool water.

pH Decreasers

Water with a pH level of 7.8 or higher is considered to be too basic. In this state, the water is beyond its saturation point and scale will begin to form on the surfaces of the pool. As with acidic water, basic water can also feel harsh to be in; causing dry skin and red, irritated eyes.

Along with reducing pH, pH decreasing chemicals can also be used to decrease alkalinity if added slowly over the course of a few days. Water with a high alkalinity will slowly increase in pH and will heavily resist efforts to lower its pH. In order to fix your pH problem, you therefore first have to lower its alkalinity.

Calcium Hardness Increasers

Water with a low calcium hardness is below its saturation point and will therefore try to saturate itself by drawing minerals out of the surfaces of your pool. This can cause things like the plumbing and jets to become brittle and prone to cracking and breaking. Pools with high calcium hardness, just like with high alkalinity, are above saturation point and will cause scaling buildup. Unlike with pH or alkalinity, there is no chemical product that can reduce calcium hardness. The only way to lower calcium hardness is by replacing a portion of the water with high calcium hardness with water that has significantly lower calcium hardness.

Controlling Algae & Other Contaminants

Keeping your pool balanced and properly sanitized will go a long way toward preventing common water problems, but sometimes your pool needs a little extra help. Algae, fine particles, metals and minerals can all affect the appearance and condition of your pool water and surfaces. That’s where specialty chemicals can come in handy.

Algaecide

Algaecides are designed to control algae growth in your pool. While proper chlorine levels and circulation are your first line of defence against algae, an algaecide can provide additional protection, particularly conditions are favourable for algae growth (such as periods of heavy pool use or during extended bouts of hot weather).

Algaecides are commonly added in small amounts on a regular basis to break down the protective outer coating that algae blooms grow, making it easier for your sanitizing chemicals to kill them. If you do start to notice the water turning green, higher doses of algaecide alongside a shock treatment will generally fix the problem before it gets out of hand.

Clarifiers

Pool clarifiers help remove very fine particles that can make your water look dull or cloudy. They work by causing tiny particles that are too small for your filter to easily capture to bind together into larger particles. Once grouped together, these particles can be more effectively removed by your pool’s filtration system.

Clarifiers can be useful when your pool is slightly cloudy or when you want to give already-clear water that extra sparkling appearance. They aren’t a substitute for proper filtration and water balance, but they can be a helpful tool when fine debris is causing water clarity issues.

Stain & Scale Prevention

Stain and scale prevention chemicals help protect your pool surfaces from minerals and metals that may be present in the water. These products work by coating mineral and metal particles; keeping them from grouping up into larger deposits that can form on the surfaces of the pool. They can be particularly useful in areas where the source water contains higher levels of calcium hardness, minerals or metals.

While stain and scale prevention products can help manage these problems, maintaining proper water balance is still important. Regularly testing your water can help identify mineral or chemical imbalances before they turn into larger issues.

Wrapping Up

Understanding what your pool chemicals actually do makes it much easier to maintain healthy, balanced water. From sanitizing the water to controlling pH and preventing scale or algae, each chemical plays an important role in keeping your pool in great shape.

With regular testing and the right chemical maintenance program, you can spend less time troubleshooting your water and more time enjoying your pool!