Pool Genetics

By Dennis Berkshire

Even with today’s sophisticated pool equipment and systems, some aquatic centers still struggle with water-quality problems.


If a facility is not appealing to the eyes and nose, such problems may result in a revenue loss as the public takes its fitness and recreation dollars to a competing venue.

It is important to remember that a swimming pool has its own ecological balance that is affected by both genetic makeup as well as environmental influences. Successfully operating a healthy swimming pool with good water quality requires a systematic approach to addressing all of the pool’s components.

Six primary factors contribute to water quality:

• Pool-water circulation

• Pool-water filtration

• Water chemical balance

• Chlorine efficacy

• Pool hygiene

• Pool lighting.

Understanding a pool’s genetic makeup (equipment and systems) will go a long way in determining what areas may or may not be affecting water quality.

In a recent phone conversation, a facility operator said he needed assistance in solving a water-quality problem caused by the filter system and based on information provided by the chemical supplier.

In another meeting, a different client asked for help solving his cloudy water problems caused by the water chemistry. When asked how he determined that the chemical system was the culprit, he revealed that the filter supplier told him.

In both cases, the actual causes of cloudy water were not what the pool operators thought. It is common for operators to turn to suppliers for advice only to realize the latest solution offered does not solve the problem.

Water-quality symptoms are usually divided into four categories:

• Turbid water

• Cloudy water

• Foul-smelling water

• Dull or hazy water.


Turbid Water
Let’s revisit the example with the client who thought his water-quality issues came from the filters. Over time, staff members purchased and used several filter-aid products, but could not achieve clear water.

A turbidimeter determined that the water in the pool had a Nephelometric Turbidity Unit (NTU) reading of more than 2.5. The turbidity at the pool surge tank revealed an NTU reading of 1.5. The turbidity of the water before entering the pool filters was 1.5 NTUs. Lastly, the turbidity after the use of filters had a reading of 0.4 NTUs.

Based on these facts, it was concluded that the pool-filtration system was working perfectly in removing the particulate as intended. In examining the other pool systems, it was discovered the cloudiness was actually caused by a deficiency in the pool-circulation system that could not transfer the solid particles to the filter system so they could be removed.

Cloudy Water
At a community-college facility, pool operators requested assistance with the chemical-treatment systems, as they were convinced the cloudy water was caused by a malfunctioning system; however, a full panel of tests determined the system was working properly.

But when the pool operator demonstrated his backwash procedure, it was apparent the filter system was not being backwashed at the minimum flow rate required to effectively clean the sand bed. The filter sand was so full of oils and carbonates that the sand would form into shapes like snow balls.

It became evident that the filter sand had become so contaminated that the filter media rate was exceeding 20 gallons per minute per square foot, and all subsequent dirt was returning directly into the pool, causing cloudy, turbid pool water.

After replacing the filter media and re-engineering the backwash system, the filter was able to provide the expected water clarity and quality. Ironically, the filter had been in place for almost four years and had never backwashed properly. It took all that time of improper backwashing for the filter to become overloaded and stop filtering the water!

Improper Water-Chemistry Balance
Another common culprit of cloudy water is improper water-chemistry balance. If the water is imbalanced, the saturation level of certain chemicals--such as calcium--can be exceeded, causing the cloudy water.

After conducting a halogen demand test at an athletic club that had depressed oxidation potential levels, it was determined the pool water was operating at a chlorine deficit, and needed to be hyperchlorinated to more than 120 parts per million. The staff closed the pool for this procedure and used 65-percent calcium hypochlorite as the chlorinating agent.

After this chlorine dissolved, the pool water not only became cloudy, but looked like skim milk by the next morning. Given the high content of calcium, the high total alkalinity, and the high pH of the water, the calcium was no longer soluble, and was dropping out as solid calcium carbonate.

After performing a test to determine the amount of acid required to bring the poolwater pH to under 7.5, staff members began adding muriatic acid. Within 10 minutes, the fog lifted and the pool water was crystal-clear.

Although most pools do not have problems this dramatic, this is a common cause of cloudy water in a calcium-hypochlorite chlorinated pool.


Examine Chlorine Levels
In determining the reason for cloudy water, one of the first questions to ask is whether there are adequate, active chlorine levels in the pool water. Chlorine demand clouds, for example, can occur due to a total lack of chlorine or due to combined chlorine compounds rendering the chlorine residual non-effective in the pool water.

In many cases, the onset of an algae bloom in pool water is preceded by cloudy water conditions, which can be indicative of a chlorine deficit. A simple chlorine demand or halogen demand test can be used if the standard chlorine test kit analysis fails to show a chlorine condition causing the cloudy water.

For pools with oxidation reduction potential (ORP) control, the relationship between test kit chlorine residual readings and the level of ORP can be used to help determine if there is a chlorine efficacy issue.

Dull Or Hazy Water
Pool hygiene conditions also can be a cause for cloudy water. This does not refer to bathers taking a shower before swimming, although this can influence water quality and overall chlorine use; rather, hygiene refers to actually cleaning the pool water and surfaces of dirt, body oils, and other pollutants.

Every morning at the same water park, workers noticed the crystal-clear water was murky by noon. After evaluating both the pool water chemistry and the filtration system, tests concluded that the problem was the amount of dirt and debris at the bottom of the river.

These pollutants would settle overnight--resulting in clear water every morning--but once the swimmers entered the water and began stirring up the dirt, the water became cloudy. The facility solved the problem by purchasing several robotic cleaners that vacuumed the dirt and debris overnight.

Cloudiness does not only affect outdoor pools, however. It is not uncommon for indoor pools to have an overall murky or lackluster appearance.

This is may be caused by the natatorium’s lighting. Without adequate lighting, the light rays cannot penetrate the water to provide the glistening water look that is so inviting to patrons. A challenge to indoor lighting is to have light fixtures that provide good light distribution that can also be serviced.

This can be achieved by a host of new lighting products, including new LED light fixtures. The use of greater levels of underwater lighting can also assist in achieving pristine water quality.

With a clear understanding of the genetic makeup of pool equipment and systems and how they are related, pool operators can be on their way to not only solving water-quality problems, but creating an atmosphere that prevents problems from occurring in the first place.

Dennis Berkshire is senior associate at Aquatic Design Group, a Carlsbad, Calif., consulting firm which specializes in the programming, planning, design and engineering of competitive, recreation and leisure-based aquatic facilities. Visit www.aquaticdesigngroup.com for more information.