Continuing my series on cloudy pool water, today we deal with a cloudy pool after shocking. A common problem that I hear from a lot of people - after adding granular chlorine, aka pool shock, the water turns cloudy, "milky white" even.
There is the tendency to blame the pool shock, and in some cases it is the quality or type of pool shock, but more often the cause of cloudy pool water is a reaction to a reaction. What I mean is, when pool chemical levels are out of whack or minerals and metals are high, adding a dose of pool shock can do all sorts of wacky things. The reaction of the chlorine creates other reactions - and knocks normally dissolved substances out of solution, causing them to become visible.
In most cases, a cloudy pool after shocking is temporary, and should clear up in a day. Keep filtering, and add a clarifier to help the filter.
5 Reasons Why your Pool is Cloudy after Shocking
1. High pH and/or High Alkalinity: When pH is above 7.6, half of the chlorine is wasted. It's best to shock a pool with a low pH range of 7.2-7.4. Alkalinity is closely related to pH, and when it's too high, it can prevent you from lowering your pH easily, and it can easily throw off bicarbonates and make the pool cloudy. Use pH decreaser to reduce Total Alkalinity if the level is over 100 ppm.
2. High Calcium Hardness Levels: If you live in a hard water area, as many do - with tap water over 500 ppm of hardness, you may want to avoid using Calcium Hypochlorite pool shock, which adds about 5 ppm for each pound of cal hypo used. Shocking with cal hypo (which is most brands of basic pool shock), can cloud the water in a pool with a high level of calcium hardness. The best range for pools is 180-220 ppm.
3. High Cyanuric Acid Levels: Another white powder that dissolves into the pool water when it's added, or builds up from using stabilized chlorine tablets, cyanuric acid can come out of solution when very high. Test your cyanuric acid (stabilizer) level every month or two to be sure that it doesn't rise above 50 ppm.
4. Filter or Pump Problems: If your pool is cloudy immediately after shocking, it's not a problem with your pump or filter, but if your circulation is poor, or the filter is dirty or too small, or if the pump doesn't run long enough each day, all of these can create a problem with cloudy water.
5. Shock Type: Calcium hypochlorite, aka Cal Hypo is the most economical type of granular chlorine, to manufacture or purchase. It also has the most calcium and binders that do not readily dissolve. In terms of making a pool cloudy, Cal Hypo is often the shock type mentioned when people ask me why the pool turned cloudy after shocking.
Non-chlorine shock, aka monopersulfate or MPS, is a quick dissolving pool shock that won't cloud pools, and lithium hypochlorite, aka "Lithium", is also very fine and clean burning, with very little residue. Assure Multi-Shock is a modified pool shock that not only shocks the pool but clarifies the pool water. Eclipse3 Emerge is another non-chlorine shock, with clarifier to prevent clouding after shocking.
As I mentioned at the beginning, in most cases a cloudy pool after shocking is temporary, and will clean up overnight. To help things along, make sure that your chemistry is balanced, run the filter 18-24 hours daily, and add a clarifier to help coagulate suspended particles so that your filter can trap them.
SPP Pool Expert