For a swimming pool owner, a chlorine smell to her pool's water can be an indicator of a chlorine imbalance. However, often the case is that the chlorine smell emanating from a swimming pool doesn't necessarily mean there's too much chlorine present. In actuality, a chlorine smell in a swimming pool isn't due to an excess of chlorine but rather to an excess of chloramines. And chloramines in a swimming pool typically mean that there's not enough useful chlorine available.
Chloramines in a swimming pool are the byproduct of an insufficient chlorine disinfection process. When there's not enough working chlorine in a pool, what there is of it binds with ammonia and nitrogen-containing compounds, producing chloramines. Those ammonia or nitrogen-containing compounds are found in human sweat and even urine, all of which frequently end up in a pool. Chloramines will increase what's called combined chlorine in a pool. And if a pool's combined chlorine is high, chlorine smell results.
The first step to take in addressing a swimming pool's chlorine smell is to measure its free chlorine and total chlorine levels. A good all-purpose swimming pool test kit will measure both levels to determine the pool's combined chlorine level. The standard formula for determining combined chlorine is this: Total chlorine minus free chlorine. Free chlorine is the working chlorine available for pool disinfection duties. And if a pool smells like chlorine, there will normally be very little free chlorine present.
Addressing the Smell
Once you've determined that your swimming pool has a high combined chlorine level, you will need to reduce it. High combined chlorine isn't desirable in a pool, so you must increase free chlorine by shocking your pool, which means raising the level of free chlorine available for disinfection. You raise chlorine in a pool by adding actual chlorine to it, usually to about 10 parts per million (ppm).
Carry out pool shocking at dusk or in the early evening. Sunlight is an enemy to chlorine, so limit pool chlorine's exposure to it whenever you shock your pool. Once you've raised the pool's chlorine level to at least 10 ppm, let the pool sit until there's about 2 ppm of free chlorine, as measured by a test kit, in the water. Free chlorine will now be in the water, and chloramines will disappear.
Effective pool chlorination to control combined chlorine and chloramines also depends on proper pool pH balance. If you don't keep your pool's pH between 7 and 8 (7.4 to 7.6 is ideal), available chlorine in the pool may work poorly or even disappear. After shocking your pool, measure pH and restore it to proper balance. Pool chlorine itself is high in pH, meaning you'll have to lower your pool's pH by adding muriatic acid (MA) according to directions.
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