by Rob Cox, August 6, 2010
Help! I can't get my pool to clear!
It's a common question this time of year. We see it in our forums, emails, chats, product questions and other areas where we answer pool technical questions.
It usually goes something like this: "I have done everything, and I mean e v e r y-thing to this pool. Balanced it, Cleaned it, Shocked it - even running the filter 24/7 and the darn thing won't clear up - Help!"
If you have ever been in this situation, with balanced pool water, good chlorine and pH levels, but it just won't clear up, you know how frustrating this can be. Every trip to the pool store costs you more money, and it seems like it will never turn around. But it will - here's some things to consider.
1. If the pool is still green, you will need to shock the pool again. Before shocking, adjust the pH level down to 7.2 or so. Lower pH helps your chlorine work better. Shock until you get a blue-grey color. Then brush the pool thoroughly.
2. If there is a lot of debris still in the pool, or on the floor - it will be difficult to clear the water until most of the organic matter is removed. We're trying to kill the algae, and if other competing organic material is in the pool, it "distracts" our chlorine from acting on the contaminants making the pool cloudy.
3. Your pool water may be contaminated. See our blog on Phosphates and Nitrates in Pools. Use of a Phosphate Removal chemical can be the magic ingredient sometimes. In other cases, where a pool has very high levels of Phosphates or Nitrates, or has had repeated algae blooms over time, it may be advisable to drain a portion of the pool water, and refill with fresh water (well water can be a source of contamination).
Pool water that has not been changed in years can become somewhat "choked" with dead algae cells, and other micro-contaminants, especially pools that have had repeated, annual algae blooms. Because of this, we recommend changing pool water every 5 years if poor water conditions develop. Water is cheaper than chemicals, I like to say - but please make sure that you are using proper pool water discharge methods.
4. Your pool filter may be undersized. Most above ground pools are installed with an adequate pump and filter system. It does the job when the water is clear, but make larger demands on the filter and it struggles to perform. Small cartridge filters just cannot do very well with turbid water. Clarifiers can help - but if you add too much clarifier, it acts as a dispersant, rather than a coagulant.
Another method that can be used is to "Floc" the pool with a flocculent such as Aluminum Sulfate (ALUM). Adding a flocculent will settle most suspended debris to the bottom in a thick layer. You will need to have a method to vacuum the settled flocculent to waste, as it clogs up filters very quickly. Using alum can be a quick fix to a troubled pool, turning it crystal clear overnight. But you may still need to address issues with Filtration, Sanitation or Circulation, they key to Clean & Clear pool water.