When And How Often To Shock A Pool (5 Reasons)



No one contests that pool shock is a highly effective method for sanitizing your pool.

But, how often to shock a pool is a hotly debated issue in the pool owner community.

Yet there are certain times when shocking is an absolute must when you have to get your pool water back in line.

Why Shocking Is Important

Unfortunately for pool owners, you can’t just fill up a pool with water and expect it to always be clean.

Due to outside influences, the state of pool water is constantly changing, becoming increasingly grimy with each passing second.

It’s for this reason why an array of chemicals are added to pool water. With the addition of a sanitizer such as chlorine, the water stays clean and safe for people to swim in.

Even though pools have a constant sanitizing agent in the water, over time it breaks down and slowly becomes less effective. At this point you need to add more of it if you want the pool to remain clean.

The idea behind pool shocking is to quickly raise the free chlorine level in the pool, killing off bacteria, algae growth, chloramines, and other pathogens in the water. This can be done using either chlorinated or non-chlorine pool shock.

Chlorinated pool shock is the most common. It gives the pool a massive dose of chlorine, killing everything in its path.

Non-chlorine pool shock is an oxidizer that attacks organic contaminants in the water. By focusing strictly on those, it “frees up” the free chlorine in the pool so it can be more effective in sanitizing the water.

When To Shock Your Pool

As stated earlier, there will be times where pool shocking must be done outside of your regular maintenance routine.

1. You Can Smell Chlorine

Pools that reek of chlorine are trying to tell you something: they are lacking in chlorine. This may seem counterintuitive as they’re giving off a pungent chlorine pool smell

But what you’re actually smelling are chloramines. Chloramines are created when free chlorine reacts with ammonia in the water. This mixture is also known as combined chlorine, which gases off and floats on the surface of the water.

Chloramines are an irritant and hazardous to humans – causing red eyes, itchy skin, nasal and lung irritation, and respiratory issues.

So if your pool is really stinky, it’s also really dirty. Shock it ASAP!

2. There Was A Surge In Pool Use

People love a good pool party. Your pool, on the other hand, not so much.

Pools should be shocked after heavy usage. This is because people are gross and bring a lot of nasty things into the water.

Seriously though, people introduce a ton of organic pollutants into a pool – oils from your skin, sweat, hair, sunscreen, and lets not forget about the dreaded urine and fecal offenders.

With an uptick of swimmers in the pool, the chlorine has to work extra hard to keep it all clean, resulting in a more rapid depletion and consumption. 

3. There Was Heavy Rain

A pool’s chemical makeup can be easily upset, and even a rainstorm can throw things out of whack.

Rain is usually slightly acidic. Technically speaking, rain should decrease the water’s pH level. However, alkalinity will step in at this point and keep the pH from taking a massive nosedive.

But heavy rain will load the pool with contaminants from the air (ie. mold spores, wind-blown debris, insects), and also dilute the pool water, upsetting its chemical makeup. 

Shocking the pool at this point is a good idea to restore diluted chlorine levels, and getting the water back in balance.

4. Your Water Temperature Soared

While pool heaters allow you to increase the water temperature to your preference, warm water eats up free chlorine like a fat kid inhales cupcakes. In addition, microorganisms and bacteria such as algae flourish in warm water.

A comfortable temperature is between 86 and 88°F. If under heavy usage, the pool temperature should be lowered to 78 to 84°F. Water temperature can also soar if your pool is in the sun all day, and you have a pool finish like stone, which naturally draws in heat.

5. You Just Opened or Closed Your Pool

Shocking upon opening or closing a pool is a must.

When you open a pool for the season, you first need to balance the water properly. Once that’s done, you’ll shock the pool to sanitize and oxidize it, simultaneously restoring clarity to the water.

At the end of pool season, you’ll need to shock it one final time to keep the pool sanitized during the months it won’t be in use.

How Often To Shock A Pool (Establishing A Schedule)

Aside from the “must shock” situations outlined above, how often to shock a pool is up for debate. 

The Optimal Shocking Frequency

Most pool owners will shock once every 1 to 2 weeks – this is ideally what you should be aiming for with your pool maintenance schedule.

You’ll come across various thoughts on this topic. Some people say you must shock once a week, while others are fine shocking once a month!

It’s also important to understand that you can’t overshock. 

The worst thing that will happen is the pool’s chlorine level will be temporarily spiked and then naturally burn off after a few hours of sun exposure. Another downside to overshocking is that you’ll just be wasting your money.

However you do need to be aware of the “must shock” scenarios that will steer you off your regular shocking schedule.

The Best Time To Shock Your Pool

Shocking your pool should only be done after the sun has gone down, during dusk or twilight hours. 

The unstabilized chlorine in pool shock has zero protection against the UV rays of the sun. Once it comes out to play, you can wave bye-bye to all the unstabilized chlorine in the pool.

So, when using chlorinated shock, always shock at night. This will also allow the pool to circulate the shock for a good 8+ hours, giving it plenty of time to fully clean the pool.

If you’re using non-chlorine shock (which is an oxidizer), you can shock the pool at any time of day and only have to wait 15 minutes before going back into the pool.

Ok Google, Remind Me In…

There’s no hard and fast rule regarding how often to shock a pool. 

But there is a generally accepted guideline of once every 1 to 2 weeks to keep your pool water performing at its highest level. 

As long as you stay on top of things, you shouldn’t have any problems with unpleasantness when it comes to the state of your pool’s water.

Categories: Pool Care, Pool Chemistry