Problem Solver - August 2008
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Keeping an Eye on Your Pool's Filtration

Many tasks are essential to pool maintenance, such as cleaning the pool regularly, keeping an eye on water quality and ensuring that the filters are kept clean. There is a direct correlation between the filter's effectiveness and the clarity of your pool water. If you are using sand, diatomaceous earth (D.E.) or Zeolite filters, it is necessary to backwash periodically to be sure your filter is functioning properly.

Q: Our pool water is cloudy. What can we do to fix the problem?

A: The effectiveness of your filter is the main contributor to water clarity, with chemical balance of the water playing a significant role. If the water is cloudy and the pool attendance has remained consistent, you can likely track the problem to one of the following sources. If your pool water chemistry is OK, that means it's time to perform maintenance on your filter. If the filter media is old, it may need to be replaced. Or, you may need to clean or backwash your filter.

Q: How and when do I clean my filters?

A: All types of filters work by pushing water through a porous media—usually sand or diatomaceous earth. Larger particles are trapped and separated from the water, allowing only the clean water to return to the pool. The gauge pressure is lower when the filter media is clean, allowing water to pass through freely.

As the debris builds up in the media, the pressure increases and it is more difficult for the water to flow through the filter. While the frequency can vary greatly, industry standards recommend backwashing when the filter gauge is reading a pressure that is 10 pounds higher than "clean" pressure. Ask your filter's manufacturer for specific instructions on backwashing your filter.

Q: How can I be sure the backwashing is effective?

A: It is important that operators be aware of their system's ideal clean pressure differential, which was established during startup. After a thorough backwash, the system should return to (or very close to) this ideal clean pressure differential. If this differential is creeping higher over time, it is a clear indication of insufficient backwash. Other clear signs are "channeling" in the sand bed and increased backwash frequency without other cause (such as an increase in pool attendance). The best way to be sure is to measure the flow during backwash and compare this to the manufacturer's recommended minimum backwash rate, which is generally 15 GPM for every square foot of filter area. Another way to keep an eye on your system—literally—is to use a filtration system that allows you to see what's going on. Some manufacturers, for example, offer a tank that has a manway with a viewport, so that you can see exactly what is happening inside the tank while it is operating, without dismantling the system. These covers can easily be retrofitted to existing compatible filters. With the view inside, you'll be able to spot channeling before it becomes a problem, and confirm balanced flow during filtration and backwash as evidenced by a smooth, level sand bed throughout the cycles.

Q: How can I conserve water?

A: There are many steps you can take to conserve water. One crucial step is to pay close attention to any leaks and take care of the problem as soon as it appears.

Believe it or not, the best way to conserve water consumed during backwash is to ensure the backwash rate is high enough. Insufficient flow leads to more frequent, incomplete backwash cycles. It is much more efficient to backwash at a higher rate for a shorter time. Also, many facilities can save water simply by waiting longer before backwashing. These facilities might backwash on a time schedule regardless of pressure differential. An additional benefit of longer cycles between backwash is that a sand bed actually removes finer particles when partially loaded (just prior to a backwash).

Proper maintenance will also help you conserve water, by increasing the time interval between draining and refilling your pool. Your filtration system will last longer if you regularly use an automatic pool cleaner. By doing this, you will not have to backwash as often, conserving more water.

Paragon Aquatics,
a Division of Pentair Water Pool and Spa Inc.:
888-KDI-SWIM (534-7946)