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Why does my pool shock not function? An expert’s simple solution

Every pool owner has experienced it: thousands of gallons of disgusting green water because you forgot to chlorinate your pool, went on vacation, or just ran out of time.

A small pool shock usually clears the pool quickly. Sometimes, however, the shock simply isn’t strong enough to move the algae. After adding shock, you wait a day or two and nothing transpires.

Fortunately, there are a few simple solutions. I spoke to a pool specialist and got a virtually foolproof procedure, along with some secret advice for those few occasions when the traditional repair falls short.


Fortunately, there is a very simple explanation for why pool shock doesn’t work most of the time. It’s all related to the pH of your pool.

Rafi Friedman, a pool specialist, informed me that a pH balance is ideal for pool shock to perform optimally. The shock won’t work if the pH of your pool is too high or too low. Before shocking, your pool’s pH should ideally be between 7.2 and 7.4.

The pH imbalance in your pool is often caused by high CYA levels. CYA, sometimes referred to as cyanuric acid, is a substance that stabilizes chlorine, extending its useful life. You may have less chlorine if you don’t have enough CYA. However, as its name suggests, it is acidic, which might reduce the pH of your pool and have an impact on chlorine.

How can I adjust a pool’s pH to make the pool shock function properly?

The pH of your pool may be easily adjusted. “If the pH of your pool is too high, you should add an acid—I suggest sodium bisulfate—to bring it down. If the pH is too low, you should use an alkaline substance like sodium bicarbonate, or baking soda,” said Rafi.

Although that’s really just branding, you can obtain sodium bisulfate on Amazon and pool bicarb at Home Depot; domestic bicarb like this one from Walmart is similar and less expensive.

It is not too difficult to add these compounds. According to Rafi, “Good pool test kits will include dosing guides that will help you decide how much to add to bring things back to neutral by taking into account the size of your pool and its current pH.” Try a little amount first if you’re not sure how much to add, and then increase as needed.

I have no problems with my CYA and PH, but my pool is still green. Any suggestions?

Green algae on the stairs of a swimming pool

(Photo courtesy of Getty Images Plus / iStock / BackyardProduction))
There are further actions you may do if you’ve tried everything above and it’s still not functioning. While it is evident, it is simple to overlook the first. To move the algae into the water, be careful to brush the walls and floor. The algae may have been dead from the shock but adhered to the walls if you haven’t brushed them down.

In addition, make sure the pump and filter are operating correctly. Even when the shock is operating, the majority of the algae may still be passing through the filter.

There are a few more possible problems if none of them resolves the issue. Green water is typically caused by copper. Chlorine causes copper to oxidize, turning your pool green. Check the label if you use shock in addition to algaecide. Your algaecide may be the cause of your issue if it contains copper. Attempt to use a copper-free In order to assist eliminate germs, some pools additionally have devices that add a little amount of copper to the water. But, you’ll need a metal remover like this one from Home Depot if the pool has an excessive amount of copper.

Controlling the levels with a phosphate remover like this one from Walmart might help decrease cloudiness since high phosphate levels—beyond 500 parts per billion—give algae a good food source. That said, it should not be an issue if you are able to completely destroy the algae.

Also, you need to apply a flocculant such as this one from Lowe’s. Flocculants may assist reduce cloudiness by clumping fire particles together. The algae might be dead and suspended in the water. All of the algae will be collected by a flocculant into a sediment that is easily vacuumed out of the pool.


Sadly, you’re out of luck if all of this seems like too much effort. “Using a completely different pool sanitation system is probably the best way to avoid having to shock your pool,” explains Rafi. Without using any chlorine, you may sterilize your pool with anything like saltwater or UV light.

That sounds fantastic in principle, but to install a new cleaning system, you would have to completely rebuild portions of your pool. Even though shock might be difficult to operate, it’s still the most effective method for clearing a murky, green pool.


Is Pool Shock Permanent?

Pool shock may indeed wear off. In around a month, liquid chlorine starts to lose its potency. Granular shock has a considerably longer lifespan—roughly five years—but it may become wet and lose its power to clean your pool if the bags it’s in disintegrate.

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