How Often Should I Shock My Swimming Pool?

pouring pool shock into a pool

You’re a clean freak through and through, and that extends to your pool — from skimming to vacuuming to filter cleaning to water testing, you’ll do everything you can to keep your pool clean. So, how often should you shock your swimming pool to ensure the water is in its purest state? The quick answer: Once a week. But, as other situations arise (more on those below), you may have to shock your pool a little more often.

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But First, What Is Pool Shock?

Blue bottles of liquid pool chlorine
Photo Credit: Maksym Kozlenko / Wikimedia Commons / CC BY-SA 4.0

Typically made of unstabilized chlorine (although, there are non-chlorine shock treatments on the market, too), shock is basically a heftier dose of this pool chemical that eradicates bacteria and rids the water of other impurities like sweat, sunscreen, urine, and chloramine. Also known as combined chlorine, chloramines are a byproduct of chlorine responsible for irritating eyes, drying out hair, fading swimwear, and causing that strong chlorine smell.

Normally, the amount of free chlorine in your pool will take care of disinfection. However, when free chlorine levels dip below total chlorine, it means there’s too much combined chlorine (which doesn’t disinfect) and there’s not enough germ-killing power to keep sanitizing your pool water to make it safe for swimmers.

To restore your pool’s sparkling clean water, shop for pool shock at your local pool store, or use one of the following types of chlorine shock:

  • dichlor
  • calcium hypochlorite (cal-hypo)
  • liquid chlorine (bleach)

Note: Some experts recommend against dichlor, as it can cause your stabilzier levels to surge, leaving your pool water with way too much cyanuric acid. And, if you have a saltwater pool, skip the cal-hypo altogether; it will cause too much calcium buildup, which can ruin your salt cell.

Liquid chlorine also comes in the form of a household chemical you most likely already have on hand: bleach. It contains the same chemical as pool chlorine (sodium hypochlorite); you’ll just need to use a larger amount than you would if using one of the shock types above.

Another choice is to use a non-chlorine shock, which works as an oxidizer to eliminate contaminants like the ones listed above; it does not kill bacteria, though.

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How Often Should You Shock Your Swimming Pool?

In addition to when you open and close your pool, experts generally advise shocking your pool once per week. Weekly shocking, as part of standard pool care, helps keep pollutants and chloramines (aka combined chlorine) under control. If you don’t use your pool on a daily basis, you can probably get away with shocking it once every two weeks.

That being said, other conditions may arise requiring an extra shock treatment:

When You Notice a Strong Chlorine Smell

The smell of summer? More like the smell of chlorine that’s attached itself to some nasty contaminants. This buildup of chloramines/combined chlorine levels swiftly sends your pool’s free chlorine level into a nosedive, and to restore its proper balance — between 1 and 3 parts per million (ppm) — you must shock your pool.

When There’s Cloudy Water

Poor pool filtration, lots of organic contaminants, and imbalanced pool water chemistry are three cloudy water culprits. To determine if this is the cause of your problem, retrieve your handy-dandy pool test kit, and check your pH levels, alkalinity, calcium hardness, and total chlorine. If the free chlorine levels are way below the total chlorine levels, that means there is combined chlorine that needs removing. 

Pro Tip: Total chlorine equals free chlorine plus combined chlorine. 

Before/After a Pool Party or Other Heavy Use

If, like a clichéd phrase, your pool has been a bit overused of late, what your pool needs is an increase in free chlorine levels to kill off infectious bacteria and other contaminants — following a surface cleaning with your skimmer, a thorough vacuuming, and a good scrubbing of the pool walls and floor.

If You See Algae Growth

While algae itself won’t harm you, it is a food source for bacteria that can. Besides that, algae can also damage your pool filter, pool pump, and pool surfaces. Restore a safe swimming environment with pool shock, supplemental chlorine tablets, and algaecide.

During Extreme Heat

UV rays evaporate chlorine from a pool, rendering these pool chemicals ineffective. On top of that, when the heat index is high, your pool water will be warmer, too, inviting all sorts of growth — from bacteria to algae — and the depleted chlorine levels won’t be able to keep up.

After Heavy Rain

Heavy rain can also wreck your pool water, throwing alkalinity, chlorine levels, and pH levels out of whack. Shock the pool to supercharge the chlorine, so it can get back to fending off all the bad stuff.

The Best Time of Day for a Pool Shock Treatment

As part of your regular pool maintenance, shock your pool weekly or biweekly after sunset. This way, UV rays won’t be able to evaporate any of the chlorine, and it’ll be allowed to work its magic killing all sorts of contaminants.

FAQ About When You Should Shock Your Pool

Can you shock your pool too often?

While you can’t necessarily shock your pool too many times, you can use too much shock at once. For every 10,000 gallons of pool water, you’ll want to use one pound of granular shock; if you pour in a lot more than that, it can take longer than 24 hours or so for the chlorine levels to drop to one that’s safe for swimmers (between 1 and 3 ppm).

Can you shock a saltwater pool?

Short answer: Yes. But some pros say since the salt cell uses super chlorinate to constantly disinfect the water, you only need to shock a saltwater pool if you notice algae growth, rather than shocking it weekly as you would a chlorine pool.

Before adding shock, turn off the saltwater chlorine generator. The best bet for a saltwater pool is liquid chlorine shock, as dichlor can mess with your stabilizer and cal-hypo can cause too much calcium buildup, potentially harming your salt cell system.

When to Hire a Professional

For pool owners of all experience levels, shocking a pool is an easy DIY job. That being said, this type of regular maintenance isn’t exactly fun, so hiring a pool care pro near you to take on the task instead may be much preferred. They’ll stabilize the water chemistry, clean the pool, evaluate your pool for any damage, and make repairs as necessary.

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Andréa Butler

Andréa Butler is a writer and editor. And while she hasn't been blessed with DIY skills herself, she is adept at writing and enjoys sharing home improvement tips and pool care guides for the true DIYers out there.