Pool water turns green because of algae in the water. Algae can grow rapidly, particularly when it's warm like Summer, which is why it can surprise you overnight. This generally comes down to an imbalance or lack of chlorine in the water.
A pool turns green when there is algae in the water. There are several reasons why algae could grow, but it is most commonly caused by prolonged exposure to the sun, rain and temperature spikes. These factors affect the chemical balance of the pool and result in the pool turning cloudy and/or green.
Is it Safe to Swim in a Green Water Pool? Short answer – it depends. Lakes contain a full ecosystem, complete with aquatic life that feeds on bacteria and toxins. This makes swimming in green water in nature safe.
When the levels are properly balanced, chlorine will keep the algae at bay, but the water will slowly begin to turn green as the algae take over if there's not enough. But be careful—adding too much chlorine in pool water can cause those metals to oxidize and turn the pool a different shade of green.
If you suspect swimming pool algae is making your pool water green or cloudy, check the water's alkalinity and pH balance. This is the most common cause of green pool water. Unfortunately, algae can become resistant to chlorine and sanitation because of the water's pH and alkalinity.
The only thing that kills algae is CHLORINE (or your sanitizing product, or one of the copper-based algaecides on the market). You need to raise the level of your chlorine – shock the pool – and maintain that high level until all the algae is dead. This may take 3 to 4 days. RUN THE FILTER 24 HOURS A DAY.
The use of baking soda in pools can spot treat algae
No one ever wants to see algae build up in their swimming pool. It can turn any backyard pool murky green or cause unsightly black spots on the walls and floor of any swimming pool.
ADD POOL CLARIFIER
The change in your pool water colour means that you have successfully eliminated the algae and can now clean it out of your pool. If your water is still green, wait another 24 hours and redo the steps from Days 1 and 2.
Green or Dark Green Pool Water:
This means there's a medium amount of algae in your water and you'll need to triple shock your pool. Triple shocking requires 3 pounds for every 10,000 gallons of pool water.
What happens if too much shock is added? You cannot overshock a swimming pool or add too much. Adding too much shock or overshocking your pool will kill off algae. The negative of adding too much shock is it will upset the chemical balance of your pool.
Keep your pump and filter running. Give the shock a good 12 to 24 hours to work it's magic. If the algae hasn't cleared up after 24-48 hours, clean and brush the pool and add another shock treatment.
The presence of too much algaecide can lead to a foamy pool water. Small bubbles will begin to be produced as the water is pushed through the return jet and back into the pool. Do not confuse these bubbles and foam with another common problem, which is air in your pool lines.
In theory, if you have a cloudy swimming pool, you can add chlorine to “shock it” and clear things up. Chlorine will get the job done. But, the amounts may vary and you may have to really pound the pool with chlorine to get the water totally clear.
Algae can be very slippery, causing swimmers to fall resulting in bumps, bruises, cuts and even broken bones. Don't try to swim in a pool that's full of algae. Besides causing injuries, an algae infested pool creates a higher risk of drowning for those who are not expert swimmers or those who fall unconscious.
Bleach, like any other kind of pool treatment, is best used in specific concentrations -- that is, you'll want to be able to detect a certain amount of chlorine in your pool water. Too little, and you won't effectively sanitize your pool water and surfaces. Too much, and your pool water might become too harsh to use.
Household bleach, Clorox and liquid chlorine can all be used to sanitize a pool. They are all types of chlorine. Household bleaches such as Clorox usually contain about 5-6% available chlorine, about half that of pool liquid chlorine. Household bleaches often have unwanted fragrances and colors.
Low pH water will cause etching and deterioration of plaster, grout, stone, concrete and tiling. Any vinyl surfaces will also become brittle, which increases risk of cracks and tears. All of these dissolved minerals will hold in the solution of your pool water; which can result in staining and cloudy pool water.
The last thing you want to do is vacuum algae manually, which will contaminate your filter. Your pool will not clear up. In fact, the chances of your problem getting worse are very high. You'll also need to vacuum to waste when there is a large amount of debris or leaves in the pool, usually at opening.
It's important to note that you should not try to vacuum green pool water until you have removed any and all organic debris using a pool net, and have added the proper chemicals to the water, and done proper brushing so that the green algae has visibly settled to the bottom of your swimming pool.
Grab a brush and some baking soda. Bicarbonate, the active ingredient in baking soda, is an effective spot treatment to help kill the algae and loosen it from the wall. Make sure you really get every last particle free; black algae has particularly long and stubborn roots which makes it a persistent strand.