An Unapologetically Extensive Guide to Pool Chemistry
Owning a pool can be a joy—imagine that beautiful summer day with sparkling blue water and happy kids splashing about. But the pool can also be frustrating, especially when it comes to the cost and time spent on maintenance.
At Together Energy, we help you save 25-40% on pool costs by optimizing how you manage your pool.
TLDR; Get chemistry right to save $
The key to clear water usually isn’t more filtration time, but better water balance
It's all about having enough chlorine to prevent "baddies"
First priority: Total Alkalinity helps maintain stable pH
Then: a stable of 7.2-7.6 means chlorine is more effective and lasts longer
The right level of CYA (sunscreen) prevents chlorine breaking down in the sun
If salt is low, your chlorinator will struggle to make enough chlorine
But if you get it "just right", your water should stay balanced and greatly reduce your pool's running cost
Why is it so hard to keep your pool water clear?
Some pools easily stay sparkling clean, while others quickly turn cloudy or green, no matter how long the filter runs.
The key to clear water usually isn’t more filtration time, but better water balance. Yes, “balanced water” sound like a pool shop euphemism for selling you expensive chemicals, but in reality, keeping your pool’s water balanced makes all the difference and will save you money. [check the price of chemicals, some pool shop franchise chains seem to charge a lot more for the same stuff].
In this guide, we’ll walk you through the essentials of pool water chemistry so you can maintain ideal levels and avoid the hassle of constant trips to the bank and pool shop.
The good news? If you balance your water correctly, you’ll only need to add a few chemicals here and there throughout the year and there'll be far fewer "green days" to worry about.
Most importantly it also means reduced filter run time, saving energy and money.
Let’s get started....
Testing Your Pool Water
Whether you use test strips or drop kits, you’ll always be measuring chlorine and pH. The commonly available 4-in-1 test strips also measure alkalinity and stabilizer (cyanuric acid), while 6 or 7-in-1 strips include calcium hardness and free vs. combined chlorine.
For salt levels, phosphates, and copper, a visit to the pool shop once or twice a year is a good idea - the salt test strips are expensive and not very accurate.
For your weekly maintenance, a 4-in-1 test strip will be sufficient to keep everything in check.
Chlorine: The Killer App
In Australia, most pools are either saltwater with chlorinator, or freshwater with added chlorine. In both cases, chlorine is your pool’s main sanitizer and the most important factor in maintaining clean and safe swimming water.
Chlorine kills bacteria, algae, and viruses by damaging their cell membranes and preventing them from multiplying.
[Bromine is sometimes used as a sanitizer, but in Australia this tends to be limited to spas. Magnesium pools are effectively the exact same as saltwater pools and once the water goes through the chlorinator cell, they produce the same chlorine as the sanitizer].
Chlorine doesn’t last forever in your pool. It gets used up as it sanitizes, and it is also broken down by the sun’s UV rays. This is why you always need to be adding chlorine to your water, either as added chlorine or by operating your chlorinator.
The recommended level for free chlorine (the active form that kills contaminants) is between 1-3 parts per million (ppm).
Types of Chlorine:
Free chlorine: The chlorine available to sanitize your pool. This is what you want more of.
Combined chlorine: is chlorine that has already reacted with contaminants, often associated with that distinct “public pool” smell. High combined chlorine levels mean your pool probably needs more free chlorine to continue sanitizing, so contrary to popular belief, if you smell that "chlorine smell" [which is not chlorine], it’s a sign you should add more, not less.
Total chlorine: This is the sum of free chlorine and combined chlorine, but it isn’t as useful a measure on its own.
So make sure you focus on Free Chlorine and not Total Chlorine when you test.
How to Adjust Chlorine:
To increase chlorine levels: Run your salt chlorinator at a higher output (if you have a dial) or if already at the maximum level, for longer. If you don’t have a salt chlorinator, you can add chlorine in liquid, granular, or tablet form.
To decrease chlorine levels: Reduce the chlorinator’s output (reduce hours, then dial down), or allow sunlight to naturally break down the chlorine over time.
Note: this post is not about minimizing your pump-chlorinator run-time, we cover that in other posts.
STOP THE PRESS: before cranking up your chlorinator, read the rest of this post. A small adjustment elsewhere can significantly impact free chlorine and save you using more electricity and wasting money.
pH: Ignore At Your Peril
The pH of your pool water is not a chemical in itself, but a measure of how acidic or basic your water is. The ideal pH range is 7.2-7.6, with 7.4 being perfect for both swimmer comfort and chlorine effectiveness.
When pH is outside of this range, problems arise. Low pH (too acidic) can cause eye and skin irritation and corrosion of your pool equipment. High pH (too basic) can lead to cloudy water, scale formation, and reduced effectiveness of chlorine.
Why does pH matter for chlorine? Free chlorine in your pool is combination of two compounds: hypochlorous acid (HOCl) and hypochlorite ions (OCl⁻). HOCl is 70x more effective as a sanitizer than OCl⁻, and breaks down more slowly in sunlight.
What determines the % HOCl and OCl-? You guessed it, pH.....
At 7.0-7.4, there is much more HOCl than OCl-, at higher pH levels, OCl⁻ dominates, and your free chlorine is less effective and shorter lasting.
So maintain a pH of 7.2-7.4 to maximise chlorine effectiveness, save on your pump's runtime, and save money and the environment.
Note: pH in saltwater pools will drift up over time, so even if you start the season perfectly balanced and your chlorinator does a great job in 3 hours per day, the pH will eventually drift above 7.6, the sanitizing potential will drop, the Free Chlorine will burn-up more quickly in UV, and you'll leave the door open for algae. That's why you always want to keep a close eye on pH.
How to Adjust pH:
To reduce pH: Add dry acid (sodium bisulfate) or liquid hydrochloric acid (also known as muriatic acid).
To increase pH: Use sodium carbonate (soda ash).
Total Alkalinity: pH's Stable Partner
Total alkalinity (TA) is a measure of your pool water’s ability to buffer pH changes. In simple terms, it helps prevent the pH from swinging up or down too easily. If TA is too low, even small changes in chemical levels or rainwater can cause drastic shifts in pH, making it difficult to control. On the other hand, if TA is too high, the pH can become resistant to change, and your water may turn cloudy.
The recommended TA range is 80-120 ppm. Within this range, your pH will remain stable, which means fewer chemical adjustments overall.
How to Adjust Total Alkalinity:
To increase TA: Add sodium bicarbonate (baking soda).
To decrease TA: Add muriatic acid or sodium bisulfate in small amounts, keeping an eye on pH levels since these will lower pH as well.
Cyanuric Acid: Your Pool's Own Sunscreen
Cyanuric acid (CYA), also known as stabilizer or pool sunscreen, protects chlorine from being broken down by the sun’s UV rays. For saltwater pools, the ideal range is 30-50 ppm.
Don't be fooled by the label though - too much CYA makes chlorine ineffective, so stay within the recommended range.
Some granular chlorine or tablets (DiChlor or TriChlor) contain CYA, so be mindful of overuse. Too much is definitely not good.
How to Adjust CYA:
To increase CYA: Add cyanuric acid.
To decrease CYA: No shortcuts here, only the dreaded Dilute Pool Water / Drain / Refill.
Calcium Hardness: Protecting The Surface
Calcium hardness measures the concentration of calcium ions in your water. Low calcium levels can cause your pool’s concrete or grout to erode (slowly but surely), while high levels can lead to scaling. The ideal range is 200-400 ppm. It does not apply to plastic or fibreglass pools.
How to Adjust Hardness:
To increase calcium hardness: Add calcium chloride.
To decrease calcium hardness: Again, the dreaded Dilute Pool Water / Drain / Refill.
Salt: The Chlorinator's Best Friend
In saltwater pools, the chlorinator breaks down salt to produce chlorine through electrolysis. If salt levels are too low, your chlorinator won’t operate effectively to produce enough chlorine.
The optimal range is typically 3,000-4,000 ppm—check your chlorinator’s manual for specific guidelines.
To increase salt levels: Add pool-grade salt.
To decrease salt levels: No shortcuts again - Dilute Pool Water / Drain / Refill.
Doing It In The Right Order
Balancing pool water in the correct order ensures smooth adjustments without unexpected side effects. Here’s the recommended sequence:
Total Alkalinity (affects pH stability)
pH levels
Calcium hardness
Cyanuric acid (CYA)
Free chlorine
Salt levels
By following this order, you’ll keep your pool water balanced, ensuring a clear, safe swimming environment all season long.
We're not far from launching TED and we want to help you save money. Join our waiting list and we'll offer you a great deal when we launch.
Comments