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Understanding the different methods of adding chlorine to a pool

By Staff | Apr 13, 2016


A swimming pool in Florida is as common as a kitchen sink, but there is more than meets the eye in the care for them.

To save money in the upkeep of pools and keeping them clean of bacteria and algae, residents employ their own strategy of chlorine treatment, without actually knowing how the chemicals they are adding is affecting their source of enjoyment.

One Sanibel resident who does know the complexity of caring for a pool is Rick Ranieri, who has a Ph.D. in organic chemistry and has worked in the field for over 30 years.

Ranieri sees many mistakes people make when they care for their own pools, either by following bad advice or not doing their research.

“Many people are not comfortable with pool chemistry and I can help by summarizing it with four, simple methods,” Ranieri said. “I list them with pros and cons and try and keep it as simple as I can.”

One of the most common misnomer people make is listening to the advice of adding a gallon of bleach a week to a pool.

“It’s not needed,” Ranieri said. “There is already chlorine in the pool.”

The smell people associate with a pool is also usually a myth.

“The chlorine scent people think they smell, is not chlorine, but the byproducts reacting with the waste,” he said. “If there is that funny smell, people think there is too much chlorine in the pool, when in fact* the levels are not where they should be, they are too low.”

The top advice, though, Ranieri gives is if you don’t have a solid understanding of what pool chemistry is all about, let a professional handle it.

“If you want to save money and do it yourself, hire a professional for the first couple of months, watch and learn of what they do and ask them questions,” Ranieri said.

Ranieri’s summarization deals with the main methods by which chlorine is added to a pool.

“Chlorine is, by far, the best way to sanitize and control microbial growth in a pool and chlorine levels should be maintained between two to five ppm,” he added.

There are four ways chlorine is introduced into a pool: bleach solution, chlorine tablets, granular sodium chloride (NaCI) and chlorine gas.

The bleach solution is very alkaline and has a very high pH level.

“The pros is it’s a cheap and easy-to-use liquid,” Ranieri said. “The con is it’s an addition of bleach to a pool, the pH may go above the normal acceptable range of 7.2-7.8. If this occurs, acid (muriatic/hydrochloric acid or sodium bisulfate) must be added to the pool to lower the pH to the acceptable range.”

Chlorine tablets are used to give chlorine some resistance to sunlight decomposition. Ranieri said the pros is it increases the lifetime of chlorine in a pool, but the cons include releasing cyanuric acid (stabilizer) which does not decompose like chlorine does.

“Over time, cyanuric acid levels build up in the pool and will lead to a condition called ‘chlorine lock’, eventually making the pool chlorine ineffective as a sanitizer,” Ranieri said. “The pool must be drained and refilled to remove the excess cyanuric acid.”

Granular sodium chloride, or salt pool, is not a sanitizer. It is converted by electrolysis to bleach, the active sanitizer.

The electrode hook-up, along with sensors in the pool, automatically perform this function.

“Minimal effort is required and it’s fairly cheap,” Ranieri said. “You just have to add bags of the (product) until the pool is at the proper level. But the water will have a somewhat slippery or briny feel to it due to the constant presence of salt. Acid addition may be required to lower the pH to acceptable levels.”

Chlorine gas requires the bubbling of toxic chlorine gas, normally kept in metal cylinders, into the pool until the proper chlorine level is reached.

The procedure is very concentrated.

“The chlorine, on being bubbled into the bottom of the pool, reacts with water to give, among other things, hydrochloric acid,” Ranieri said. “This lowers the pH and may require the addition of soda ash to bring the pH up.”

There are different pros and cons to add chlorine to a pool, with many different levels of costs with each one, as well, but if a pool owner doesn’t know the complexities of adding chlorine to it, going the way of a professional is the way to go.