Solving Cloudy Water Mysteries

Here’s a water condition that neither the amateur nor the expert can figure out. Can’t, that is, until she or he knows a lot more about the pool and its environment than does any swimming-pool wizard who might walk up to your pool simply to observe the water...

Cloudy water, no doubt, is the nemesis of many a pool operator. It so often seems to have an un-detectable and mysterious source. ‘Truth is, there're probably a dozen sources – at least four of which are quite common, and the resulting water looks the same, lousy.

Here’s a list of my favorite reasons for pool-water turbidity, and some of what to do about them. Could any of these be the cause for your cloudy water: organics, failing paint, precipitation, diatomaceous earth, failing plaster, entrained air, other suspension, and sabotage. That motel pool with crystal clear water all week may, for any of these reasons, cloud up substantially over the busy football weekend, not to clear again 'till Tuesday.

Maybe the most common cause for turbidity is just plain dirty water. That’s organic material you’re looking at, or it’s the products of the incomplete oxidation of suspended organics, and it means you’re not oxidizing near’ well enough in your high-load pool.

Notwithstanding such causes as the nearby rice-field burning or the neighboring dusty, windy construction site, poor oxidation in any pool water will eventually allow cloudiness to develop. Remember that the filter's job is to handle the big particulate and the non-oxidizables; your chemical oxidizer has the far greater job in producing polished water than the mechanical straining performed by the filter.

The chlorine product (or other “oxidizer”) must handle the organic solids introduced into, and suspended in, your pool. If your ORP is impaired in any way, by high pH, dominance of chloramines or excessive stabilizer, the oxidation process may be slowed by an order of magnitude (1/10th!) or more. Cyanuric acid alone, for example, can reduce the equivalent ORP of 1 ppm “free” chlorine to that of an un-stabilized .2 ppm. And that’s at only 20 ppm CYA! More stabilizer? Enjoy your cloudy pool.

So I hope your pool is automated by a device that measures and controls the oxidation potential of whatever sanitizer you’re feeding. Setting a value of 780 to 800 mV will cause a feed of, well, whatever it takes to oxidize those suspended organics and clear up that pool. And go easy, please, on that Cyanuric Acid stabilizer!