Are you ready to be shocked at how easy this is?
That’s right: shocking your pool is pretty straightforward once you’ve understood the basics.
In this guide, we’ll cover:
- What shock treatment is
- Why you should use shock treatment
- When to shock your pool
- Types of shock treatment
- Step by step instructions to shock your pool
- Other chemicals for pool maintenance
What Is Shock Treatment?
“Shocking your pool” is when you add a chemical (chlorine or other) to it to re-balance the water chemistry. Sometimes the product used is called “pool shock”.
“Shock” may sound alarming, but it’s called this because the process immediately upsets the existing water and begins to clean it.
Shocking your pool is also called super chlorination, or reaching breakpoint chlorination.
To reach breakpoint chlorination, we focus on two things:
- Free chlorine: the level of actively disinfectant chlorine (keeping it between 1 and 3 ppm).
- Combined chlorine: the chlorine in the water that’s already been used (keeping it under 0.2ppm).
Breakpoint chlorination is when the active chlorine starts to get rid of the used-up chlorine to look after your pool again.
You’ve reached it when you have about ten times the amount of free chlorine than combined chlorine.
Why Use Shock Treatment?
It’s better to shock your pool than to shock your guests with a grubby pool!
Shocking is the ultimate cleansing and refreshing of your pool water. It’s like hitting the ‘reset’ button on an electronic device.
If something is a little out of whack, shocking is like going back to the beginning and starting over.
Shocking is particularly important for keeping out nasty bacteria and algae growth. Not only can this cause allergic reactions or irritation to swimmers, but it can also make surfaces slippery and start to clog your filters.
If you have an algae problem, you’ll need to alter your shock preparation depending on the stage (colour) that your algae has progressed to: whether it’s light green, dark green, or black-green algae will determine your level of shock.
When To Shock Your Pool
There are a few instances when you might want to shock your pool.
1. Every week for routine maintenance
Don’t wait until you have itchy eyes!
A diligent pool owner would shock their pool once a week. The average pool owner would do it every other week.
But of course, it depends on your usage. The more often you take a dip, the more often you should use shock.
2. When you smell chlorine
That classic off-pool smell that we’re all thinking of right now is often blamed on chlorine.
However, it’s actually a build-up of chloramines, resulting from chlorine mixing with sweat, urine, and other bodily fluids that we’d rather keep out of pools.
The process of shocking gets rid of these chloramines.
3. When you open/close your pool to cleanse it of bacteria
Freshen it up before you go in if it’s been a while!
Equally, shock it before you cover it for a season. It will prevent the build-up of bacteria while you’re not using it.
4. After a storm/heatwave
Shocking is also a good way to rebalance the water chemistry after a heavy event, like a party where lots of people entered the pool, or a storm where lots of rain and debris have landed in your pool.
If you’re worried about something affecting the content of your water, think about pressing that ‘reset’ button.
Types Of Shock Treatment
Most types of shock are chlorine, although we’ll also touch on a non-chlorine option for you.
The following three types of shock treatment must all be used after dusk so that the sun doesn’t burn off any of the unstabilised chlorine.
No one should enter the pool for eight hours following the shock treatment.
Recommended by Dolphin Pacific: Focus Shock ‘n Clear.
- It contains between 50% and 60% chlorine.
- It doesn’t need to be dissolved beforehand.
- It’s versatile – it can be used as regular chlorine and as a pool shock.
- Its active ingredient is sodium dichloroisocyanurate.
Calcium Hypochlorite (a.k.a. Cal Hypo)
Once, this was the most popular form of shock.
- It contains between 65% and 75% chlorine.
- It must be dissolved before being added to water.
- It adds calcium, so be careful if your pool water source is already rich in calcium.
This one will be a little more expensive and harder to find due to the rising prices of lithium that is usually reserved for manufacturing batteries.
- It contains 35% chlorine.
- It doesn’t need to be dissolved beforehand.
Also once a popular option for shock dosing
- It contains 13-15% chlorine when fresh
- It can be added straight to the pool
- Loses strength over time – quite quickly!
- Will damage clothing on contact
The difference between chlorine shock and non-chlorine shock is basically the time you must leave your pool before entering again!
If you’re looking for a quick fix because you have people coming over for saussies on the barbecue, a non-chlorine shock like potassium peroxymonosulfate is probably for you.
The pool will be ready in 15 minutes after adding this directly to the water.
We recommend Focus Clean ‘N Swim.
How To Shock Your Swimming Pool
Now that we’ve covered the why, let’s dip into the how, starting with the tools you’ll need.
- 20 litre bucket (if required)
- Pool shock (product).
- Stirring stick.
- Rubber gloves and eye protection.
- Closed shoes and old clothes that you don’t mind getting bleached if splashed.
- Water test strips or a kit.
What to do before shocking the pool
- Check your pH and alkaline levels to make sure they’re balanced.
- Prepare your equipment.
- Reread this guide and the instructions on your shock product!
Note: Always follow the instructions on the pool shock product itself. This is just a guide.
- Wait until the sun goes down in the evening, and make sure your pool filter system is on and running.
- Test your pool. This will determine how much combined chlorine is already in your pool water, and therefore how much shock you need to add. The shock product will have instructions on how to calculate with this information, or you can use a chlorine shock dose calculator.
- Mix/dissolve the shock if it needs mixing. Do this by adding the water to the bucket first, then the shock, then stirring it thoroughly. The approximate measurements are 0.5kg of shock to 20 litres of water, but follow the instructions on your bag of shock.
- Pour the bucket of shock mix into the pool evenly as you walk around the edge of the pool. Try to minimise splashing.
- Leave the shock in the pool overnight for at least eight hours.
- Check the chlorine levels the next morning.
- Wear a chemical resistance mask, goggles, and gloves, and try not to breathe in the chemical air directly.
- Never mix types of pool shock! If you’re about to finish one bag and start the next, make sure you add them separately. Don’t just combine them.
- Free chlorine levels should be 3ppm or lower before you go swimming again.
Other Chemicals For Pool Maintenance
We know from our Ultimate Guide to Pool Cleaning that shock is not the only product you need to look after your pool and keep it in a healthy state.
Other chemical levels also come into play, and you need to consider using them:
- Sanitiser: to kill bacteria.
- Balanced pH level of 7.4-7.6: use pH reducer and pH and Alkalinity increaser.
- Calcium hardness: to control scaling and corrosion.
- Algaecide: for when you get into trouble with algae.
- Clarifier and flocculant: a quick fix for cloudy water.
- Metal sequestrant: for rust coloured stains.
If you’re a little rusty yourself, check out some more of our cleaning tips.
Great – you’re all set to shock your pool and enjoy hours of water fun!
How much chlorine do you need to shock a pool?
Usually, a chlorine level of between 10ppm and 30ppm is sufficient to combat algae, chloramines, and bacteria.
How long until you can swim after you shock a pool?
If you’re using a chlorine shock, it’s necessary to wait at least eight hours before using the pool again. Add the shock treatment at night to prevent chemical disruption from the sun, and the pool should be good to go again in the morning when the chlorine levels have returned to 3ppm.
How do you shock a pool that is green?
Follow the same process and products for shocking any pool, but add algaecide treatment as well.