Problem Solver - August 2007
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Maintaining Consistent Chlorination

What can we do to ensure consistent chlorination for our commercial pool?

There are all kinds of indicators that might signal a problem with chlorination, though some of them can have multiple possible causes. Cloudy water or an algae bloom can be related to chlorination problems, as can surface growths, which are felt by swimmers as a slippery, slimy surface. Another sign of a problem is difficulty maintaining a chlorine residual. If you're using more and more chlorine, that could be because you've been inconsistent in the past and your facility has developed some kind of infestation. Finally, measurements that indicate a high combined chlorine level also indicate a problem. This is caused by sweat, urine and various other sources of organic amines or ammonia in the water. When this nitrogen-containing matter reacts with chlorine, it produces combined chlorine, or chloramines. When a pool has developed an infestation or high combined chlorine level, you may need to shock the pool at least once to fix the problem, but it's much better to avoid such problems, especially infestations of algae blooms, in the first place.

One key step to take to ensure your chlorine levels remain consistent is simply ensuring good maintenance. Keeping the pool clean and vacuuming it regularly are essential. Make sure the chemical feeders are refilled frequently enough to avoid running empty and that they are operating properly.

You also need to ensure your filter is well-maintained. The media should be fresh enough to be usable, and you need to backwash at the right time. Read the operators' manual and follow the manufacturer's guidelines. In addition, a commercial pool that is open for operation should keep its filter pump running 24x7. That's because you don't get any filtration unless the water is moving through the filter. Plus, you need the pump to be running to ensure proper addition and dispersal of chlorine and pH control chemicals.

The clearer you keep your water through good filtration, and the more consistent you are at maintaining chlorination levels, the easier it will be to maintain good water quality. Though codes vary from one place to another on recommended chlorination levels, the typical recommendation is a free chlorine residual in the water of 1 to 3 or even 4 parts per million. If you're too close to the low end, you may end up with a combined chlorine problem.

In addition to proper maintenance, regular testing is also very important. Commercial pools generally are regulated by local health ordinances that mandate a specific frequency of testing and, sometimes, record-keeping as well. But whether required by the authorities or not, it's a good practice. You should test the water at least once every couple of hours, because chlorine demands change throughout the day. For example, you may need to adjust chlorine output in peak sun hours or during peak bather load hours. You should regularly test your chlorine levels, both free and combined, as well as pH. You also should test alkalinity and calcium hardness, though these tests can be performed less frequently.

Those tests will become even more useful if you keep good records. Even if the health inspector in your area happens to not care, record-keeping is a smart idea and can provide additional protection if a lawsuit comes up. It also can help you solve problems as they arise, or even anticipate and adapt to problems you've seen in the past. For example, if your chlorine tends to fall at a certain time or day or during a specific month during the year, you'll be better prepared to deal with it if your records show you when you can expect that problem to start.

One other way to make sure your chlorine levels are consistent is to use automatic feedback control for chlorine and pH. The controller on the chlorinator will regularly test the water electronically, and the measurement is used to automatically control the operation of the feeder. This can help provide exact and timely additions of chlorine to deal with fluctuations.

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