For 32 years, the voice of the pool and spa service professional.

Water clarity begins with good filtration

By Marcelle Dibrell

When it comes to water quality, the pool and spa service professional has two goals: making the water safe and free of any disease-caring bacteria, and ensuring that the pool and spa looks inviting. 

The first goal is usually accomplished by employing some type of sanitizer. For the second, adequate filtration to remove solids that are not only unsightly but worse, can interfere with the disinfection process.

Because while it may be acceptable for the local pond or watering hole, suspended solids make swimming pool and spa water look cloudy, murky and unappealing. 

When a pool or spa filter is operating at maximum efficiency and used in conjunction with proper chemical treatment, the properly sized filter will help to keep pools both safe and sparkling. 

Filters eliminate the small suspended particles to make the water visibly inviting. Because even if you can show your customers that the water is safe with a test kit, not many people will want to dive in if the water is cloudy, dull or dirty looking. Water clarity is important for a number of reasons. 

In addition to simple aesthetics, the increased visibility afforded by a good filter provides for a safer bather environment, with less of a drowning risk. Consumers may not be aware that numerous drowning have occurred simply because the victim was not clearly visible through cloudy water.

But in addition to the drowning risk, cloudy water can help to facilitate an algae bloom, or be a sign that one has already begun.

Cloudy water can also be a sign that water balance parameters have gone out of control.

For these reasons and more, it is essential to ensure that water clarity is maintained, and filters accomplish much of this important task.

Filter performance is determined by the clarity or turbidity of the water. The National Sanitation Foundation sets pool water quality standards in nephelometric turbidity units measured with a nephelometer. The standard for public pools is 0.5 NTUs, although up to 1.0 NTU is allowed for up to 6 hours. 

For residential pools, which do not have to conform to NSF standards, water clarity is generally determined visually. The rule of thumb is that the water has good clarity if “heads or tails” is visible on a coin tossed in the deep end.

But regardless of the coin, if the water appears cloudy or hazy, there’s a problem requiring remedial action beginning with chemical testing. If proper water balance and sanitation has been maintained, the filter may be improperly sized, improperly maintained, or not given adequate filtration time.   

In this issue, we provide information about filtration, including some of the design elements and operational specifics.

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