Keep That Green Murk Out of Your Pool

by Pool Builders on 01-04-2011 in Articles

Green pool water is almost always due to algae, though excess copper from an ionizer or flow-driven metallic sanitizer (like Nature2) might turn it a clear greenish color. Once algae begins to grow in a pool, it rapidly overwhelms the system, going through a light green to darker and darker shades of murk. Algae can double every 12 hours or less, depending on conditions. The pool becomes unusable quickly, and not just for aesthetic reasons. Algae can harbor unhealthy levels of infective bacteria.

Algae can have several causes, but the primary one is inadequate sanitizer. In the majority of pools that use chlorine as the primary sanitizer (including pools that use salt chlorine generators), this means there is not enough free available chlorine (FAC) in the water. For most pools, this would be 2 to 3 ppm, assuming "balanced" pool water.

What Can be Done About Algae?

An ounce of prevention is worth a pound of cure. Swimming pool algae is a perfect example of one of Ben Franklin's most famous aphorisms. As you will see below, getting rid of algae once it is established in your pool is an onerous process. You should prevent algae formation if at all possible. There are two solutions to algae, the first one based on prevention, and the second based on cure.

Prevention: Maintaining Clean Water Prevents Algae

Preventing algae formation is a lot easier than the cleanup after it is established. Basically, you need to keep your water clean and well-sanitized continuously, and the algae will not form. However, if you are sanitizing your pool using traditional chemicals, this can be a lot of work in itself, with chlorine, stabilizer, algaecide, pH balancers, and other chemicals always in flux.

We suggest a simpler alternative (assuming you begin with clean water):

  • Install an ozone generator on the water circulation line downstream from the pump according to manufacturer's instructions. DEL Ozone offers pool ozonators for all sizes of residential pools.
  • Maintain free available chlorine (FAC) at the.5 to 1.0 ppm level to circulate continuously in the pool (heavy bather loads may require more).
  • Test frequently at first for pH (balance should be 7.2 to 7.6 - add an acid like muriatic acid or an alkalai like soda ash to achieve this) and chlorine (add as needed). With experience, you will learn how often and how much chlorine to add, in part determined by how you use the pool.

Enjoy your pool!

Cure: Getting Rid of Algae

Once algae takes hold, a chemical assault is required to eliminate it. The ozone generator cannot remove high concentrations of algae growing in the pool (especially those organisms attached to the pool walls) because the ozone is mostly destroyed in the disinfection process before the circulation water reaches the pool. Only a small residual level of ozone remains at that point, usually not enough to penetrate the nooks and crannies of the pool - that's what the background FAC is supposed to do.

Here's what you need to do to get rid of algae:

  • Adjust the pH to the normal range, 7.2 to 7.6.
  • Brush the pool walls and bottom to loosen attached algae.
  • Make sure the pool filter is clean, and turn on the pump. Keep it running throughout the process.
  • Shock the pool with a chlorine-based product. This may require 2 or 3 times the normal amount of shock - read the product instructions.
  • Add an algaecide along with the shock. Some algaecides are meant to be used in conjunction with shock, and some are not compatible with chlorine or ozone and may stain the pool, so read the label carefully.
  • Test and monitor the water, repeating the shock process every 12 to 24 hours until all algae is dead and discolored.
  • Although the dead algae will begin to settle to the bottom of the pool, adding a flocculent (floc treatment) will help the algae particles coagulate, making cleanup and/or filtration more effective.
  • Vacuum the pool and check the filter. Clean the filter if possible, but this algae-killing cure often overwhelms a filter, so replacing it may be the best course.
  • Include an algaecide in your chemical routine, and shock the pool once or twice a month to prevent future algae outbreaks.

Enjoy your pool!

Avoid the Cure: Install an Ozonator

If you prefer swimming in your pool to cleaning it, find the right pool ozonator for your pool, clean the water once, and then maintain it with ozone and an adequate amount of background chlorine. A benefit of this method is that your pool water will be and feel fresher with fewer chemicals, and you will also avoid the problems with noxious byproducts of chlorine like chloramines.

Maximize the Ozone Power

It is important to note that the ozone is injected in the pump flow, and only when the pump is running. For adequate sanitation and disinfection, DEL Ozone, the world's leading innovator in ozone sanitation applications, recommends running the main pump at least 6 hours per day, depending on the pool's recirculation rate (turnover).

However, the pool ozonator could be running 24 hours per day for maximum sanitation and disinfection power. With today's energy-saving variable speed pumps often mandated for in-ground pools because of energy requirements, this can be a limitation because most manufacturers' ozone generators work only on the high speed. Luckily, DEL Ozone offers a variable-speed injector manifold that will work with any pump speed, so both energy savings and maximum pool ozone effectiveness can be achieved.

Enjoy the Pool More!

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