How Long After Shocking a Pool Can You Swim In It? (Surprising Answer)



Shocking is a necessary part of owning and maintaining a pool, but it can put your pool out of action for longer than is ideal.

If you’re thinking about shocking your pool (or have already done so) and want to know how soon after you can start using it again, this article will break it all down for you.

Quick answer: It’s recommended to wait between 8 and 24 hours for the chlorine to fall back down to normal levels. However, if earlier testing shows a chlorine level of 5 ppm or below, you don’t actually need to wait longer.

Can You Swim After Shocking a Pool?

No, you should NOT swim after shocking your pool.

At least not immediately after.

When it comes to chlorine level, most swimming pools sit steady at around 1 to 3 parts per million. This is the minimum range required to sanitize pool water while also keeping it safe enough (and comfortable enough) to swim in.

Much less, algae and bacteria are quickly allowed to take hold. Much more, the high concentrations create a serious health risk.

Since shocking a pool requires 10x the normal concentration, the chlorine level can spike to an eye-melting 30 parts per million during this process, which is far too high to be considered safe.

How Long After Shocking Before You Can Swim?

Most pool shock instructions will tell you to wait anywhere from 8 to 24 hours before swimming.

In particular, this timeframe refers to chlorine-based shock products, like cal-hypo shock, dichlor shock, and even liquid chlorine shock.

Note: This is partly why most pool owners choose to shock their pool overnight — but this timing is also to prevent the sun from gobbling up the excess chlorine before it had a chance to do its thing.

In reality, though, assuming the rest of your chemistry is properly balanced, you only have to wait until the chlorine level falls back into a safe range.

While this can sometimes take between 8 and 24 hours, it can also happen considerably faster than expected under the right circumstances, even potentially sooner than 8 hours.

What is a Safe Chlorine Level to Swim In?

What exactly is a safe range?

Well, consider this as a baseline: According to the CDC, chlorine levels up to 4 parts per million (ppm) are considered safe in drinking water.

As for swimming, most pool experts would agree that a chlorine level of up to 5 ppm is considered safe enough to swim in, and some would even argue this number to be as high as 10 ppm.

If you’re eager to start using the pool again after shock treatment, you’ll need to test the water frequently (such as every hour) to ensure it has fallen within the recommended range, ideally below 5 ppm.

Can Pool Shock Hurt You?

Yes, pool shock can absolutely hurt you.

We’re talking about a very high concentration of chlorine. Not only is shock dangerous for you in powder or granular form, but it also poses serious health risks for several hours after adding it to your pool water.

What happens if you swim in a shocked pool, you might ask?

Well, assuming you haven’t allowed enough time for the excess chlorine to dissipate, it can:

  • Damage your eyes. We all know that dry, itchy feeling from swimming in a chlorine pool. Imagine a multiple of that feeling with the prospect of developing conditions like pink eye or conjunctivitis.
  • Damage your skin. Chlorine targets your natural oils and dries out your skin, leading to dry, flakey, and sometimes flakey skin. High levels of exposure can even lead to chlorine rash.
  • Trigger breathing issues. High concentrations of chlorine in a pool can let of vapors of chlorine gas, which is highly toxic. Even trace amounts of this gas can trigger those with breathing ailments, such as asthma.
  • Turn your hair green. A combination of chlorine and metals in the water can cause your hair to turn a tint of green, especially if you have blonde hair or if you recently dyed your hair.

What About Non-Chlorine Shock?

Most pool shock treatments are chlorine-based, either in the form of calcium hypochlorite (cal-hypo) shock or Dichloroisocyanuric (dichlor) shock.

This is because high concentrations of chlorine are extremely effective at destroying algae and bacteria, as well as removing chloramines (also known as “combined chlorine“) from the water through a process called oxidization.

Non-chlorine shock, otherwise known as ‘monopersulfate’ or simply MPS, is a common substitute for chlorine-based shock, especially for non-chlorine pools and chlorine-sensitive swimmers.

One of the biggest benefits of non-chlorine shock?

It only takes around 15 minutes to dissipate, meaning the pool is ready for use in the time it takes you to change into your swimsuit (well, almost).

Be aware, though, MPS is an oxidizer. While it’s very capable of breaking apart chloramines, it’s won’t be useful in fighting against bacteria or algae. It’s also very acidic, so you’ll need to monitor your pH level after use.

Just a Little Longer…

As tempting as it is to jump in early, it’s always better to be on the safe side and wait it out just a little longer than is probably necessary.

If time is of the essence, a water testing kit will tell you exactly how soon you can start using your pool after shock treatment.

Categories: Pool Care, Pool Chemistry