A Guide to Swimming Pool Shock Treatments

Chemicals are an essential component for keeping your pool clean and safe for swimming. Implementing cleaning methods and routines is important for keeping on top of your pool's maintenance and ensuring that it's crystal clear.

However, general maintenance isn't always enough, especially if you're opening up your pool for spring or you've been away for a while. Alongside essential sanitisers, such as chlorine and bromine, other chemical treatments provide a quick and effective 'deep clean'; these are called swimming pool shock treatments.

Shock treatments are vital for maintenance routines; they effectively kill algae, bacteria, and other harmful pathogens. However, because of the nature of these chemicals, you must know how to safely and effectively use them.

In this article, we will be looking into what shock treatments are, why you need them for your pool and how to use them safely.

Discover our range of swimming pool chemicals and water treatments

What is Shock Dosing for a Swimming Pool?

Shock dosing your pool refers to a stronger concentrate of swimming pool sanitiser that instantly impacts the water and provides a deeper clean when compared to general maintenance. In most cases, shock dosing is related to concentrated chlorine, but chlorine-free shock alternatives can accomplish a similar result.

A shock dosing chemical, chlorine or otherwise, differs quite significantly from general day-to-day sanitisers. This is important to be aware of, as you will need to ensure that you're purchasing the correct chemical and using it appropriately. However, shock products are usually labelled as such; the most common version is a chemical called Sodium Hypochlorite.

How Does Chlorine Shock Work?

Chlorine is the most popular sanitiser for swimming pools and spas. Shock treatments work by immediately increasing the water’s chlorine level, allowing it to clean the pool effectively.

Using a shock treatment raises the waters "free chlorine" level. Free chlorine refers to chlorine that is yet to be combined with chlorinated water, enabling it to sanitise the water and eliminate any harmful microorganisms effectively.

Chlorine works by attaching itself to materials such as algae or dirt. This starts the process of creating free chlorine molecules, which can kill off the algae. Dosing your pool with free chlorine is essential, as it removes the combined chlorine from the pool, which builds up over time and is unable to continue its job as a sanitiser.

Once the pool's cleanliness is back on track, you can allow the chlorine levels to return to normal.

Two people’s legs splashing water in a pool

Why Do I Need to Shock Treat My Swimming Pool?

Although it may sound like shock treatments are only necessary for emergency pool maintenance, they also play an essential role in pool maintenance schedules. While general chemical balancing is vital, shock treatments are also required, particularly during heavy use.

Chlorine shock treatments are helpful against algae, while their strong cleansing properties also make them a great balancer against dirt and debris. If the pool begins to look murky after heavy use or suffers from heavy rainfall, shock treatments can effectively clean the pool before you rebalance the pool's chemicals.

When Should I Shock My Swimming Pool?

There are many reasons to shock dose your pool. It is not only an essential part of a swimming pool's maintenance schedule, but it's an effective means for tackling various pool issues, such as algae infestations, reopening your pool after a significant closure or cloudy water after heavy use.

Below, we've listed some events and reasons you'll need to shock your pool water:

  • Once a week for general maintenance when the pool is in use
  • After heavy rainfall
  • After particularly heavy use, such as a pool party
  • When reopening the pool

What Swimming Pool Shock Treatment is Best?

If you're just entering the world of pool maintenance, you'll start to notice that there's a great variety of different shock chemicals, including brands and alternatives. Which one you should choose will often depend on your circumstance, but they all fulfil a similar purpose.

Shock Granules or Liquids?

The main difference between granules and liquids is usually down to the brand as opposed to their form. As a general rule, liquids tend to be cheaper and easier to use but can have a smaller shelf life.

Granules sometimes need to be turned into a liquid mixture before being used in the pool but can be easier to keep for longer.

Granular Shock Pouches 4.8kg (16x 300g sachets)

Shock Chlorine or Non-Chlorine Alternatives

Again, the difference here is based on preference rather than their effectiveness. As with everyday swimming pool chemicals, you may choose to avoid using chlorine as it can cause discomfort for certain bathers with sensitive skin. If you already use chlorine in your pool, a chlorine-based shock treatment is more often than not a cheaper option.

How to Use a Shock Treatment Safely

You must treat all swimming pool chemicals with caution. However, given the concentrated nature of shock treatments, special care should be given.

We strongly advise that you always follow the instructions provided by the product's manufacturer. However, there are some general rules to follow whenever using a shock treatment:

Handle the Product in a Ventilated Area

Ultimately, chlorine is a harmful gas. Handling it in concentrated quantities will cause chlorine to enter the air, so you must be outdoors or in a ventilated space when using these products.

Clean the Pool Beforehand

Before administering a shock treatment, any floating items, such as leaves, should be removed as chlorine will focus on eliminating floating debris when present. Following the same theme, try to make the pool as clean as possible before using a shock.

Rebalance the Pool Before Swimming

Shock treatments provide an instant boost but can take a long time to clean the pool effectively. The designated amount of time can vary, but you must not swim in the pool until it's complete, as the chlorine levels can be dangerously high. To resolve this, most people perform a pool shock overnight.

Once the chlorine levels have returned to a safe level, the pool will likely need rebalancing. One of the most popular pool shocks, calcium hypochlorite, can cause the calcium levels of your pool to rise; this will need to be reversed when rebalancing the water.

For more information, check out our guide to water testing your pool.

How Long do You Have to Wait to Swim After Shocking a Swimming Pool?

After using a heavy granular chlorine shock, your pool will usually require 24-48 hours before the chlorine level has dropped to a safe swimming level. Lithium and non-chlorine shock labels usually allow bathers to return to the pool quickly; however, you will need to check the manufacturer's instructions before doing so.

Swimming pool shock treatments are an essential part of any pool owner's kit! Here at 1st Direct Pools, we sell a wide range of pool and hot tub chemicals, including shock treatments! Browse our range of products or contact a member of our experienced team for more information.