Cleaning Up a Summer Swamp

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The last thing any pool owner wants is to have an outbreak of algae during the summer. Well-maintained pools should be free from algae, but there are some things that can turn a maintained pool into a green menace right at the height of swim season. Here are just some of the causes of algae outbreaks in summer.

Summer Storms

Rainstorms are notorious for bringing nitrogen into pools, where the nitrogen converts into nitrates, a food source for algae. In addition, when nitrogen in the air comes in contact with raindrops, it is converted to nitric acid, which will be carried into the pool.

Flooding can cause mud and debris that carries algae into the pool. Also, if the power is knocked out and the pump cannot work to circulate water, things can get bad fast, especially in the hot days of summer.

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Pool Parties

Summer is the time for backyard pool parties. However, more people in the pool than usual (and often for long periods of time) results in higher chlorine demand. In fact, chlorine can be completely consumed within hours during a hot afternoon. This can lead to fast algae growth when the pool is packed with swimmers who bring dirt, bacteria, sunscreen and other organics into the water. Also, if guests bring their own life jackets, inflatables or even swimsuits that have previously been in a lake or river, algae can be carried directly to the pool. If the pool is not super-chlorinated, cleaned and thoroughly brushed soon after the pool party, algae can appear rapidly.


Most fertilizers contain nitrogen and phosphorous, two main nutrients for plant growth, and algae is a plant. Throughout spring and summer, we are planting and renewing the backyard. The fertilizers used for lawns and flower gardens can make their way into the pool through overwatering or even via the wind. Once the hot weather hits and chlorine demand increases, algae have plenty of nutrients to get a strong foothold.

Lack of Filtration and Circulation

Water that is moving is healthy water. Water that is still will increase the potential of algae. It is imperative during the hot summer months that the pool receives sufficient filter turnover time and good circulation. In peak swimming season, the pool should filter a minimum of six to eight hours per day. Return jets should be positioned to prevent dead spots and ensure the greatest amount of flow and movement throughout the pool.

This may concern energy-conscious homeowners. However, insufficient filtration during the summer months can lead to additional cost from increased chemicals and treatments of algaecides. Filtration and circulation are vital during and after heavy swimmer loads.

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What To Do When The Pool Has Become A Swamp

Chlorine is still one of the most effective killers of algae, so doing a superchlorination of 10 to 20 ppm of chlorine can go a long way towards wiping out the algae. Bromine has been shown to be an even faster killer than chlorine, so choosing a two-part bromine algae system in which you add the algae product and follow with a chlorine or a chlorine-free oxidizer to produce active bromine. These systems can kill algae within 24 hours. Immediately after adding chlorine or bromine algae products, it is important to follow with a clarifier to help floc and remove dead algae to the filter. The clarifier should be dosed at three to four times the normal maintenance and can continue to be used throughout the clean-up process. The pool filter should run for 24 hours until all algae has cleared. Once the algae are cleared, the filter should be thoroughly cleaned. A good preventative algaecide may be added to prevent additional outbreaks through the end of the season.

Wrap It Up With A Good Enzyme

You may have seen commercials lately showing oil companies harvesting algae. And what are they harvesting it for? Oil. Algae exudes hydrocarbon and can leave plenty of oily residue behind in pool water and in the filter media. Using a good broad-spectrum enzyme after heavy algae growth can help clean the water and surfaces. In addition, the enzyme will help break down any additional non-living organic material which could cause chemicals to degrade faster. Then proceed to your in-season maintenance program, which includes:

1. Shock with chlorine, or use a sodium bromide algae product along with chlorine

2. Follow immediately with a three to four times dose of clarifier

3. Run filter 24 hours and ensure good circulation and filtration ongoing

4. Thoroughly clean filter

5. Test and treat for phosphates if necessary

6. Add a good preventative algaecide

7. Use a broad-spectrum concentrated enzyme to clean up oil and non-living organic debris

Now the pool is ready for your customers to finish out the summer season with good quality water.


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