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Basic Above Ground Pool Chemistry

Updated: Dec 22, 2022

A beginners guide to understanding their above ground pool's water chemistry, with the Canadian climate in mind. For more experienced above ground pool owners, click here to read our advanced pool chemistry guide for all situational chemicals that won't be covered in this basic guide.

Understanding basic pool chemistry is extremely important for all pool owners. A proper knowledge of the basics will give you the ability to keep your family safe through a sanitary and optimized pool experience. Weekly at home testing using Aquachek test strips is the best way to keep tabs on your chemical levels. Supplementing at home test with a monthly trip to the pool store (bi-weekly when temperatures rise over 30°c) will be required to ensure proper water balance.

Please note that all recommended chemicals levels are specifically for vinyl above ground pools in the Canadian climate. Any potential readers with differing pool types (gunite, fiberglass, etc) in different climate zones may require different chemical levels.

Chemistry Introduction

Basic above ground pool chemistry can be broken down into the big 5.

They are:

  1. Chlorine (free/total)

  2. pH

  3. Total alkalinity

  4. Stabilizer/CYA

  5. Calcium hardness

Although the big 5 aren't the full extent of all chemicals you will ever test for, they represent the vast majority the of the time and effort both you and your pool store will be working towards in order to keep your pool in tip top shape. With proper mastery of chlorine, pH, alkalinity, stabilizer, and calcium hardness, your pool will sparkle for years to come.

What Do My Pool Chemical Levels Mean?

1. Free/Total Chlorine

Your chlorine acts as a sanitizer that kills algae and bacteria. Low chlorine levels will result in algae and clarity issues, while high chlorine can lead to liner bleaching and damage, as well as bather irritation. When chlorine levels are low, check your chlorinator or dispenser to see if you need to add more pucks, and shock the pool using a granular shock. Liquid chlorine is not pH neutral or pre-stabilized unlike granules. Therefore, granular shocks are the best choice. Free and Total chlorine levels should be the same. If they are unbalanced, your pool will need to be shocked to restore a balanced reading. If your pool has a salt water chlorine generator, you need to ensure that your pool has the proper salt level and the generator is set to the proper operating percentage (30-40% typically) in order to maintain the correct chlorine levels. Salt water pools can be "shocked" by turning the generator up to 100% for 24hrs, or by using the "super chlorinate" button.

  • Recommended Levels: 2-3ppm

2. pH

A measure of the acidity of your pool water. Levels under 7 on the pH scale are acidic, with levels over 7.6 are more basic. Acidic water can lead to extreme corrosion of pool parts, while basic water can inhibit your chlorine from working and cause clarity issues and scaling. Proper pH levels are important for keeping water comfortable and preventing itchy eyes as well. Any pool owner using a salt water chlorine generator will notice their pH is chronically basic (7.8+), as pH drift is a side effect of the salt water generation process. Salt water owners should be vigilant about keeping pH levels in check with frequent testing and application of pH down.

  • Recommended Levels: 7.2-7.6

3. Total Alkalinity

In order to stop your pH from falling out of balance, maintaining your alkalinity is required. Alkalinity acts as a buffer to your pH, so the two chemicals are intrinsically linked. Keeping pH in balance won't be possible without also balancing your total alkalinity levels. Low alkalinity will result in pH drift and corrosion, while high alkalinity will result in cloudiness and scaling. Balanced pH is extremely important in liner longevity.

  • Recommended Levels: 100-160ppm

4. Stabilizer/CYA

Protects your chlorine from the sun’s UV rays. Low stabilizer will result in your chlorine burning off in the sun before it can work, leading to algae or cloudiness. High stabilizer has the opposite effect and prevents chlorine from working properly, which can lead to cloudiness.

  • Recommended Levels: 30-40ppm

5. Calcium Hardness

As the name suggests, calcium hardness is the measure of dissolved calcium in the pool's water. The lower the level of calcium in the pool, the harder the water will feel. Chronically low calcium hardness can lead to damage to your filter sand and liner. High calcium hardness requires dilution to correct.

  • Recommended Levels: 175-250ppm

(Optional) Salt Levels

Salt levels will vary by the make and model of your salt water chlorine generator. If you do not have a salt water chlorine generator, you will not need to monitor your salt levels. Properly maintained salt levels will ensure that your salt water chlorine generator has the adequate fuel to produce chlorine. When the salt levels get too low, the generator will stop producing chlorine and clarity issues will occur. Therefore, more salt will need to be added directly to the pool in front of the jet with the pump on. Be sure to brush up any deposits left on the pool's floor.

  • 2800-3400ppm for above ground pool salt systems

Weekly Chemicals vs Water Balancers

Now that we have a basic understanding of the basic pool chemicals, we can understand how these relate to your weekly pool maintenance.

In the typical weekly chemical routine, an above ground pool owner will use chlorine shock, chlorine pucks, and algaecide. Your chlorine pucks will dissolve slowly over the week giving you the baseline chlorine required for a clear and sanitary pool. Chlorine shock will boost chlorine levels and kill bacteria and algae in the pool. Algaecide will help prevent algae from forming and/or growing. This weekly routine balances your chlorine, although it does not address pH, alkalinity, stabilizer, or calcium hardness.

These chemicals (pH, alkalinity, stabilizer, calcium hardness) are often referred to as balancers. These balancing chemicals are only ever applied as needed. By testing your water weekly using Aquachek test strips, and supplementing this by taking a monthly trip to the pool store for professional level test (when temperatures reach 30c or higher, testing should increase to twice a month) you will be able to keep tabs on the level fluctuations in your pH, alkalinity, stabilizer, and calcium hardness. When the levels fall out of the recommended range, you can apply the chemicals as needed in the order recommended by your pool store professional, or trusted water testing software. This is all it takes to look after your pool and keep your family safe.

Proper water chemistry is required by your pool's manufacturer's for continuity of your warranty. Looking after your investment is a no brainer!

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