How to Clean an Empty Pool with Algae

The winter season has passed, and it’s time for you to put your pool to good use again. However, your pool is now a shadow of its former self, looking so unrecognizable. It is filled with various contaminants from dead leaves to dead bugs and even algae! You’re definitely not filling that pool with water anytime soon. Who would want to dive into any pool looking like the one in the image below?

You probably think this might cost you a lot of money to clean, but that is very wrong. You might not have to spend a dime if you have the cleaning equipment already. But before we go into cleaning the pool, let’s do a backstory on algae and their mode of entry into pools.

How to Clean an Empty Pool with Algae

Types of Swimming Pool Algae

If you’ve ever had any experience with pool algae, you’ll know there are just three types of algae (green, yellow, and black algae) commonly found in pools. Although there are many other classes of algae, these three are the only ones that are compatible with freshwater environments like your swimming pools. Let’s explain how each of them affects your pool:

Green Algae

Green algae belong to the division Chlorophyta and undergo photosynthesis just like plants. They are the easiest of all three to eradicate from pools. You can get them out with a good ol’ scrubbing or disinfecting with chlorine.

Yellow Algae

Yellow algae belong to the class Xanthophyta and undergo photosynthesis like green algae. They are harder to eradicate than the green algae but easier to eradicate than the black algae. 

Black Algae

Black algae are not actually species of algae but belong to the Cyanobacteria phylum. They are the hardest to get rid of because they implant themselves deep into the plaster walls of pools. They require aggressive methods of elimination, such as an acid wash.

What Factors Influence the Growth of Algae?

Apart from eliminating the algae in your pool, you definitely want to know how to prevent it from happening again. Below are the factors you must take note of to ensure your pool doesn’t experience algae growth anymore:

1. Chemical Balance

The top factor that affects the growth of algae is the proportion of chemicals in the pool. Chemicals like chlorine must be adequately present so their antiseptic effect can prevent algae growth. Also, the pH must not be too high as alkaline pH favors algae growth. Also, the presence of nitrates and carbonates favor the growth of algae.

2. Poor Circulation

Stagnation of the water in the pool could also cause an increase in the growth of algae. To prevent this, you need to ensure your filter is fully functional and not clogged. A clogged filter will not filter out contaminants from the water, which promotes the growth of algae.

Other factors that could promote the growth of algae include the use of contaminated swimming trunks or contaminated equipment in the pool.

How To Remove Algae From An Empty Pool

To remove algae from your empty pool, the best method will be to use an acid mixture to scrub down the pool walls and base. This will eliminate any type of algae present.

Removing Algae With An Acid Mixture

This method is suitable for yellow and black algae because both are stubborn, and chlorine shock won’t work against both. To carry out this method, you need the following:

  • A gallon of water
  • A gallon of acid
  • A hose connected to a running water source
  • A large can with at least a capacity of 2 gallons
  • A vacuum
  • A scrub brush with a long handle
  • Protective wear and a gas mask (to prevent acid splash on skin and inhalation of fumes)

After getting all these ready, you can follow the steps below to get your pool back to a sparkling clean state:

Step 1

Use the scrub brush to scrub the walls of the pool. This helps to eliminate any debris or dirt. Also, it helps to get rid of the heads of the black algae. However, note that removing the heads does not eliminate them. As I mentioned earlier, they are deeply rooted in the plaster walls of the pool.

Step 2

Use the vacuum cleaner to get the scrubbed dirt and algae heads out of the pool.

Step 3

Wet the pool walls with water from the hose. 

Step 4

The next step is to prepare the acid mixture. First, pour the gallon of water into the large can. Then, add all of the acid into the water. Make sure you add the acid into the water and not vice versa.

Step 5

Use a portion of the acid mixture to wet a side of the pool wall and the portion of the pool base around it. Then, scrub down this part with the scrub brush to enhance the activity of the acid.

Step 6

Rinse off the acid with the water from the hose. 

Step 7

Repeat the process for each side of the wall.

If you notice the algae is still growing, you can repeat the whole procedure using a greater proportion of acid in the acid mixture.

How To Prevent Further Contamination of Pool By Algae

After eliminating the algae from your pool, there are some steps you can take to make your pool an unsuitable environment for algae. These steps include:

1. Regular Disinfection With Chlorine

Chlorine is a water disinfectant that prevents the growth of algae. However, you should know that there is a permissible amount of chlorine you can add to the pool. Its concentration should be around 1 – 4 ppm. This roughly translates to about a pound of granular chlorine per 10,000 gallons of water. Depending on the brand of chlorine you’re using, you should inquire about how regularly you should disinfect the pool with chlorine.

2. Filter Cleaning

The filter you use in your pool is vital to preventing algae growth. If you do not clean it regularly, it could get clogged. This would lead to reduced circulation of water, hence, contaminants spending longer periods in the water. The presence of contaminants leads to the growth of algae.

3. Regular Chemical Tests

The balance of chemicals in your pool is essential to making the pool environment toxic to algae. You need to check the balance of the chemicals in the pool at least twice a week. If you need to add any chemical, do so appropriately.

Of course, you shouldn’t forget regular cleaning. With these tips, your pool is sure to stay in sparkling clean condition.

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