"Heavy rain dilutes pool chemicals, especially salt and chlorine, which causes the pool to turn green. This means the water is not sanitised or healthy, so it's vital to address this.
Rainwater itself does not cause algae, but it can provide the right environment for algae. Rain will bring phosphates, nitrates and other organic contaminants into the pool. As we discussed earlier, rain also reduces chlorine levels.
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.
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.
Should the green be due to pollen, there may be little to do in the way of minimizing the discoloration short of erecting a building around the pool. Fortunately, assuming there are no allergies to the pollen, it is safe to swim in a pool with that as the cause for green water.
Shock Your Pool with Chlorine to Kill Algae
This is the main event in clearing a green pool—killing the algae. Pool shock contains a high level of chlorine that will kill the algae and sanitize the pool.
Shocking your pool isn't necessary, although, it's not a bad idea either. If you get an extremely heavy rain fall, you could shock your pool for good measure. This will help fight off any contaminants that the rain may have brought to your pool.
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.
Pools can immediately turn green after shocking when they have metals like copper in the water. These metals oxidise when exposed to high levels of chlorine which makes the pool water turn green. Adding a metal control product such as Zodiac Metal Remover will help to restore the pool water.
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.
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.
Too much algaecide can cause foaming that can damage your filter. In some cases, too much algaecide can also cause eye and skin irritation. In addition to adding algaecide after shocking your pool, you should add algaecide to your pool water when closing down for the year.
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.
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.
Give your pool a good shock treatment 1 to 2 days before the storm hits. You can bring the chlorine level up pretty high to prolong the pool being depleted of chlorine.
Rain almost immediately causes the pH (Potential Hydrogen) in the pool water to rise while also reducing the TA (Total Alkalinity) slightly via dilution. Higher pH will cause more of the chlorine in a pool to become inactive or “fall asleep” reducing it's effectiveness.
Effect on Pool Water pH
Since rain is diluting your pool, you may expect that it will reduce the acidity of your pool water. However, all rain in the US is acidic due to pollution, so rain actually decreases your pool's pH – in other words, the pool water becomes more acidic.
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.
Liquid chlorine and granular shock have the same active chemical that sanitizes your pool, what changes is the strength and the way you use it. Liquid chlorine is less costly, unstabilized and comes in liquid form. Granular shock is stabilized and comes in a solid form that dissolves in your pool.
It's often recommended to shock your pool once a week. If you don't do it every week, you should at least do it every other week. This is necessary to maintain your pool's water chemistry. If you have a lot of people over in your pool or have a party, you may want to shock your pool more frequently.