I had a friend tell me about a month ago “My pool is green and I keep shocking it but it won’t clear up. Why is that and what else can I do?” The very first question I asked him was how long has it been since you drained your pool? He proceeded to tell me it’s never been drained since he had it built eight years ago. The reality is that for all the money he’s spent on chemicals to try and clear up the pool, he could’ve just had the pool drained and filled with fresh water for the same price if not less (not including the cost of a green clean). In my opinion there are two key reasons why you should drain your pool every two to three years.
Cyunaric Acid – Cyunaric acid is a chemical found in granular form that’s added to your pool when your pool is started up and acts as sunblock for chlorine. We usually start a tablet pool with 20-40 PPM and a salt pool with 60-80 PPM of cyunaric acid. It’s also present in chlorine tablets and if there were no cyunaric acid in your pool the chlorine would be consumed too fast. Chlorine being consumed too fast hurts the water’s ability to be properly sanitized and can lead to a green pool or waterborne contaminants. It also hurts your pocket book because you continually have to add more and more chlorine to the pool.
Ironically, an excessive amount of cyunaric acid is harmful to your pool’s water. When too much cyunaric acid is present (from years of adding chlorine tablets to the pool) it forms such a protective shield around the chlorine molecule that it significantly limits the chlorine tablet’s ability to release chlorine, affecting the water’s ability to be sanitized. When this occurs, most people try and shock their pool to get the chlorine levels back up (like my friend), but they don’t realize that some forms of shock have cyunaric acid in them and rather than clearing the pool up, they actually make the problem worse.
There are a couple ways to effectively sanitize your pool if you have this problem. You can either use a type of shock that does not contain cyunaric acid like Calcium Hypochlorite (Cal Hypo) or liquid chlorine. The problem with Cal Hypo is it contains calcium. We already have a problem in Arizona with hard water and calcium, so adding more calcium to the water is not always the best decision. In my opinion if you choose not to drain your pool, liquid chlorine works great to effectively shock your pool. It doesn’t have a high concentration, however it also doesn’t add other harmful chemicals to your pool. The downside to each of these is your chemical costs will significantly go up.
Total Dissolved Solids – TDS can best be described as dissolved things in a given body of water. It’s everything in the water that’s not actually water including hardness, alkalinity, cyanuric acid, chlorides, bromides, sulfates, silicates, and all manner of organic compounds. Anytime you add something to your water it increases the TDS level. This includes not only sanitizing and pH adjusting chemicals, but also conditioner, algaecides, and tile and surface cleaners. It also includes airborne pollutants, leaves, debris and bather waste (sweat, makeup, sun tan lotion, etc) as well as dissolved minerals.
At low levels, TDS does not present a problem. In fact, a certain amount of TDS is necessary for water balance. But at high levels – above 3,000 parts per million – you are welcoming problems. TDS buildup is inevitable and evaporating water does not solve the problem. The TDS does not evaporate with the water. As TDS builds up, it diminishes your ability to sanitize your pool. You will consistently find yourself adding more and more chemicals to your pool to effectively combat the rise in TDS. Coincidently, adding more chemicals adds more TDS to the water.
Draining your pool every 2-3 years is inevitable and a part of regular maintenance. When you drain your pool, make sure it’s done in the winter time. I never drain a pool in the summer because the sun will beat up the inside of your pool causing cracks in the plaster/ pebble tech. Draining your pool consistently will cut your chemical costs down, diminish equipment malfunctions and keep you and your family healthy while enjoying your pool.