5 Reasons Why Your Pool Is Still Green Or Cloudy After Shocking

Nothing beats going for a dip in your pool on a beautiful summer day. You go to your backyard only to be greeted with a pool that looks like it’s been on a week-long bender.

That’s right. You’ve got a green pool! :(

Unfortunately, this is a scenario that occurs more often than not. Previously we have talked about How to Fix a Green Pool, where we covered the following steps to clear up your water.

1. Balance the pH and Chlorine shock the water.
2. Check the filtration system for any problems or malfunctions. Rectify if required.
3. Brush the walls and floor to dislodge the algae into the pool water. Rake up any debris from the bottom of the pool floor. Make sure all baskets are clear.
4. Backwash the filter.
5. Return the valve to the filter and turn on the pump.

Note: If you want to quickly clear sweat and urine contamination and swim on the same day, consider using OxyFresh, a non-chlorine shock treatment that makes your pool swim-ready in as little as 15 minutes!

But for some reason, sometimes the pool is still green or cloudy even after shocking. Why?!

First of all, don’t worry, sometimes pools turn green after shocking. But provided you have added enough shock to your pool, here are the most common reasons why your pool is still green and how you can fix it:

1. There might be metals in the water

Pools can immediately turn green after being shocked 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. (Note: Remember to bypass the pool heater if there is one when shocking the pool with chlorine.)

2. You used copper-based algaecides

Using too much copper-based algaecides can spike up the copper levels in your pool and turn your pool water green. Using a metal-free algaecide can prevent this from happening.

3. Your CYA (Cyanuric Acid) or pH level is out of whack

Chlorine stabilizer (Cyanuric Acid) protects chlorine in the pool from the sun’s UV rays. UV light destroys or degrades unstabilised chlorine, thus making chlorine a lot less effective. To fix this, you want to make sure your CYA level is 30-50 ppm before you add your pool shock. When cyanuric acid levels are too high, they can also prevent chlorine from effectively killing the nasties in the water. 
There’s a similar relationship between the efficacy of chlorine and the pH level of your pool. For example, at a pH of 8, chlorine is only about 25% effective! Remember to test and adjust your pH level to 7.2-7.6 before shocking your pool. (Refer to our article on How to Test and Fix Your Pool Water)

4. Phosphates in the water

Having an overload of phosphates could give algae additional food. Phosphate levels in pools should be kept below 500 ppb (that parts per billion). You can find out the phosphate levels in your pool water by taking a sample to your local pool store for testing, or you can get a phosphate test kit. We recommend using the appropriate dosage of Phosphate Remover to prevent algae from reoccurring.

5. You didn’t use Flocculants or Clarifiers

If you still can’t see the bottom after shocking your pool, you may need to add a clarifier or flocculant the next day to remove the dead algae.

Flocculant binds to small particle impurities in the water, causing them to clump together and fall to the bottom of the pool. On the other hand, Clarifier is a maintenance product used to restore shine to slightly cloudy water. They both bind microparticles into larger particles. However, the particles created by clarifiers are removed by the filtration system, whereas flocculants require extra time and effort to vacuum particles that have dropped to the pool floor.

How do you prevent your pool from turning green or cloudy again?

The answer is…………………………….

Yes, you’ve guessed it – keeping your pool clean and chemically balanced. We recommend testing your water at least once a week.

If you notice chlorine levels are a bit on the low side, add sanitiser immediately. Remember that algae is a lot easier to prevent than to remove. You can add Pool Algaecide or Supreme Algaecide monthly during regular maintenance. But honestly, your best bet is just to stay on top of the sanitiser situation. We recommend that you obtain advice from your Zodiac Pool Professional before adding any treatment to your pool or spa.