Foam & Bubbles in Your Pool Water

When it comes to seeing foam or bubbles in your pool, it’s important to make the distinction between “foam” and “bubbles.” If you see them in the water, sometimes reaching the surface, and they dissipate—never lasting very long—then those are Bubbles. Foam, on the other hand, is often described as frothy, whitish, and it tends to persist.

So, why do you see either of them, is it a problem, and what should you do, if anything? Bubbles are typically caused by the saltwater chlorinator and can generally be ignored, going away as they do.

Foam is a somewhat different story with a range of causal or contributory factors and solutions and bears a closer look.

Causes / Responses

• Accumulation of Organics: The most prevalent cause of foam is an accumulation of organics, bather’s waste, personal care products, sweat, or detergents. Treatment is pretty straightforward in that these contaminants need to be broken down, i.e., oxidized (shocked). This is a good example of when chlorine-free shock is a suitable choice since you need to oxidize these compounds but there’s no extra need for sanitation.
• Low Calcium Hardness: Low Calcium Hardness levels in pools will not cause foaming, but it does make it easier for foam to develop and persist—typically at levels of 150 ppm or less. Raising the Calcium Hardness to 200–300 ppm will suppress the development of foam and cause it to dissipate more rapidly.
• “Quat” Algaecides: Certain “Quat” Algaecides (quaternary ammonium) can cause and amplify foaming issues. They also become subject to oxidation by your Free Chlorine, further depleting the available chlorine in the pool. Switch to non-stabilized Chlorine if an algaecide is needed.
• Early Algae Formation: Early, or incipient, algae formation can also release compounds—as the chlorine kills it—that lower the pool’s surface tension, allowing bubbles to form into foam. This may very well be accompanied by an increased demand for chlorine which will bring down your FC levels. Check for phosphates in the water and eliminate them if present using a Lanthanum Salts-based phosphate remover and cleaning the filter two days after treatment.

Prevention

Bubbles, as we noted, need not worry you, but foam is unsightly and needs to be dealt with. Preventive measures are certainly called for; pre-emptively shocking the pool after heavy use, keeping a Calcium Hardness reading around 200 or higher, eliminating the use of “quat” algaecides, monitoring the Free Chlorine level, and keeping phosphates knocked out can all go a long way in making a foamy pool a thing of the past.