How to Keep Chlorine in Your Swimming Pool

by Pool Builders on 07-03-2011 in Articles

"I need to buy some chlorine stabilizer. My pool can't keep the chlorine level normal." says the new customer.

The next thing we do is ask them, "Do you have a pool water sample?"

They answer, "No. Why do I need a water sample? The pool just won't hold chlorine. I add it and it just disappears."

And so, we continue down the list of questions. The odds that this pool owner will need stabilizer - otherwise known as "conditioner" or its chemical name cyanuric acid (CYA) - are slim to none. There are many factors as to why a pool will NOT need to add this chemical. In fact, if you randomly do add CYA, you may actually compound the problem and make it worse.

Let's briefly take a look at the 3 most common reasons of why a pool will consume chlorine. Keep in mind that similar problems happen with bromine.

First off, how's the pH level? If the pH is LOW - under 7.0 or lower - your pool will naturally and chemically consume more chlorine. That's just how water chemistry works. Low pH: higher chlorine consumption and use. High pH: lower chlorine consumption. For this reason, you need to maintain a pool pH of 7.4 - 7.6 for optimal chlorine consumption and use.

Second, what's the water temperature? Most pool owners don't realize - or this fact was never explained to them - that for every 10 degree F rise in water temperature, the pool will consume DOUBLE the amount of chlorine.

For example a 10,000 gallon pool, with a water temperature of about 78 degrees, will typically (considering good water balance and lack of visible algae high bacteria levels) use about 8 oz of slow dissolving trichloro tablets or sticks in a seven day period. That will provide a consistent chlorine level of about 1.0 - 1.5 ppm. The same pool with all of the same parameters at a temperature of 85 degrees F, will use almost 16 oz of slow dissolving trichloro chlorine. If the water temperature climbed to 95 degrees (unlikely, but possible in certain parts of the country), that same pool will use at least 32 oz - that's 2 pounds - of trichloro sticks or tablets!

Now, keep in mind that the above example presumes that the pool owner - that's you - is following a good system of weekly shocking and algaecide as part of their weekly care, along with proper water balance. If you're not following a good system or program, the odds of your pool needing and using significantly more chlorine increase substantially.

Keep this information in mind if your pool has a heater or you use a solar blanket...

The third most common reason for higher chlorine consumption is usage. How many people are using the pool? If it's hot and you have the neighborhood kids in the pool every afternoon for 4 hours every day, your pool will have to use extra chlorine just to keep up with the all of that extra stuff that people bring in with them into the pool. You know, hair gel, body lotion, sunscreen, makeup. Then there are body oils, perspiration (sweat), urine, fecal matter (not to be gross, but according to the CDC, the average person has a peanut sized piece of fecal matter on their own body almost all of the time...), saliva. Plus, we haven't even mentioned trees, birds, dogs, and other flora and fauna.

All of that puts extra demand on the sanitizing system.

As you can see, there are many factors that contribute to higher chlorine consumption.

Some of these other articles will help you understand what you need to consider before you add those unnecessary pounds of Cyanuric Acid (Stabilizer or Conditioner) to your pool.

Other factors affecting chlorine consumption are:

  • Chlorine Demand - from a variety of sources including environmental as well as chemical
  • Chloramines - often times made worse from normal additions of tap water
  • Algae growth - early algae growth may not be noticeable, but it will cause you to use more chlorine
  • Cloudy water - what is the real cause of the cloudy water?
  • Bio films - bio films provide the base for many pool and water related issues.

Keep in mind that once CYA is in the water, it stays. In fact, if you're using a stabilized chlorine - dichloro or trichloro - it is constantly replenishing the stabilizer. There's usually no need to add more. Ever! Unless of course you add a lot of fresh water. Even at spring pool opening, DO NOT add stabilizer or conditioner until the water has been circulated for at least 2 days. Then test first. Add only if the stabilizer level is under 25 ppm.

Do it right. Stop shopping at the Big Box Marts, hardware stores and any other place where you can't get a professional answer.

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