Why Is My Pool Still Green After Shocking It?

Shocking your pool is a lengthy process. Heavy shocking with granular chlorine can take anywhere between twenty-four to forty-eight hours before your pool is ready to swim in. Even if you used the best pool shock, you may be left with a pool that looks like it’s never been cleaned. It’s green and cloudy, but why?

You aren’t alone–this is a common problem for pool owners. ‘Shocking’ refers to the process of adding chlorine or non-chlorine chemicals to destroy contaminants in your pool. These contaminants include algae, combined chlorine (or chloramines) and bacteria. When those contaminants are not destroyed, your pool continues to look cloudy or green.

Shocking your pool takes anywhere between one to two days before it is ready to swim in. You might even wonder how long you should run the filter after shocking the pool–that’s another eight hours, minimum. You need to provide adequate time for the filter to clean the water and for chemicals to be circulated. This can take up to an additional twenty-four hours. It’s a disappointment when it still isn’t clean after all that time, so if you just finished shocking your pool and it’s still green, there may be a few more steps for you to take.

You Need to Use Flocculants/Clarifiers

If you’re wondering why your pool is still cloudy after shocking it, you likely did not use flocculants or clarifiers. Clarifiers coagulate small particles to make it easier to clean them through the pool’s filter system. Flocculants operate similarly, but the larger clumps sink to the bottom of the pool where they can be vacuumed out.

These can be added the next day after shocking to remove any remaining dead algae.

There Are Phosphates in the Water

If you have an abundance of phosphates in your water, then your algae has an abundance of food. You want to keep your phosphate levels below 500 PPB (parts per billion) in your pool. Get a phosphate test kit to test your levels. If the levels are too high, use the appropriate dosage of phosphate remover.

Your pH or Cyanuric Acid Level is Off

Cyanuric Acid (also known as CYA or chlorine stabilizer) protects the chlorine from UV rays from the sun. Chlorine (especially when it is unstabilized) is less effective when it is exposed to UV rays. Most pools are outdoors, so this is likely relevant to your pool.

Check your CYA level before you shock your pool. The level should be thirty to fifty ppm before you add your pool shock. If the levels are higher than fifty PPM, it can prevent the chlorine from killing the bacteria and algae in the water.

This also applies to your pH level in your pool. If your pH is too high, the chlorine is less effective. Test your pH level before shocking your pool. An acceptable range for pH is between 7.2 and 7.6.

There Are Metals in the Water

Ever see an old, copper penny? They usually have some green on them. This can happen to pools as well if there is metal in the water. Metals oxidize when they are exposed to high levels of chlorine (such as shocking the pool), which results in green water. 

Luckily, there is an easy solution. Just add a metal control product during your shocking process and it will filter out the metals.

Copper-Based Algaecides

Copper is a metal, and when metals are exposed to chlorine, they turn green. Copper-based algaecides are no exception. They can also spike up the copper levels in your pool in general, which is not dangerous, but leads to green coloring in your pool. Your pool is still clean, but it just might not be visually appealing. Switching to metal-free algaecide will solve this.

The best way to avoid a green pool after a long shocking process is to test, test, test. It is recommended you test the chemical levels in your pool at least once a week. By staying on top of the chemical balances, you will have a clean and beautiful pool after shocking it!