Shocking your pool at regular intervals is important but it will not be very effective if you do not run your pool pump long enough to allow it to do its work. So how long should you run the filter after shocking the pool?
You should run your pool pump for a minimum of 6 hours after shocking, although running it for a full 24 hours after you put the shock in the pool is often recommended. This is to ensure that not only is the shock thoroughly mixed around the pool but also that the filter will remove any dead germs or algae killed by the shock.
If you shocked your pool but didn’t run the pool filter then the concentrated chlorine would not be mixed thoroughly with the pool water so you would have areas of very high concentration. Not only would this mean the shocking would not be so effective but potentially the very concentrated chlorine might damage the pool.
Also, without the pump running, and therefore the pool filter system not working, any dead algae etc will not be filtered out.
How long should I run my pool pump after shocking?
You should certainly let your swimming pool filter run after you have given your pool a shock treatment and actually while you are shocking it too. The main reason for this is that you need to ensure that the pool shock is thoroughly mixed throughout the pool water, including the water in the plumbing, pump, filter etc.
In most cases, after giving the pool a shock treatment, it will be necessary to run the pump to circulate the water for a minimum of 4 hours and often at least 8-12 hours.
I normally shock my pool in the evening and then set the timer to run the pump all night. I then test in the morning and if the free chlorine levels are still high I continue to run it.
If you didn’t run the pump afterward then there would be pockets of very strong chlorine around your pool which could damage the liner or other pool components.
Why should you shock your pool?
In order to maintain good water chemistry, it is important to raise the free chlorine level so that the contaminants in the pool such as chloramines (chlorine molecules combined with sweat, germs and other substances), and bacteria are removed. Algae growth is also prevented.
This is exactly what adding pool shock to your swimming pool does as you are adding concentrated free chlorine to bring the levels up high enough so that it can do its magic.
I generally find it more economical to buy shock in bulk in the form of a 25lb bucket of granular shock.
All of these are available on Amazon or from your local pool store.
How to shock a pool
This is the method I use to shock my pool:
- Firstly ensure the pool is clean and free from leaves and other detritus by vacuuming if necessary.
- Mix the shock in a bucket of water and stir until it is all dissolved. It may help to dissolve it all and quicker if you use hot water.
- When shocking a pool should the pump be on? Absolutely. Make sure your pump is running and if there is any air in the system make sure you bleed the pool pump
- Walk around the pool pouring the shock from the bucket around the edges of the pool as you go
- Leave the pool pump running with it on the filter setting for between 6 and 24 hours. I often split the difference and run it overnight, so around 12-15 hours.
- You shouldn’t swim in the pool until the free chlorine level (sodium hypochlorite) drops below 3-5 ppm.
When should you shock a pool?
There are a number of times when you should consider shocking your pool:
- Whenever you start up at the beginning of the swimming season and before you close it at the end it is good practice to shock a pool.
- If you have very heavy rain, this can wash contaminants into the pool. So it can be a good idea to shock the pool prior to it being used for swimming again.
- Particularly during periods of heavy use it may be necessary to shock the pool weekly. This is because swimmers and children often take contaminants into the pool with them such as sunscreen, makeup, sweat and even urine (we all know what young children can be like). These can use up the normal free chlorine quickly so shocking restores the levels.
- If after you have tested your pool water it shows that the combined chlorine reading is high then you should take the opportunity to shock the pool to restore the levels.
- If your pool has turned green due to a build up of algae then the only way to resolve it, and make the water clear again, is to use pool shock and shock it.
Can you shock your pool with bleach?
It is possible to shock your pool using bleach but generally the chlorine levels in domestic bleach are relatively low at around 5% whereas liquid shock, for example, can be as high as 15%. You would therefore need much more bleach to achieve the same result.
It goes without saying, or at least it should, that if you do use bleach you should not use bleaches that contain fragrances or colors.
How soon after shocking the pool is it safe to swim?
Different types of shock can make a difference so the first piece of advice would be to read the manufacturer’s instructions on the packaging which will advise how long before you can resume swimming after shocking a pool.
See my post for a full guide – How long after shocking a pool can you swim?
Also you may wonder whether the pool pump should be running when you swim so this article will answer that – Do you run the pool pump while swimming?
Can I put my solar cover on the pool after shocking?
You should not put the solar pool cover back on the pool immediately after shocking. High chlorine levels can degrade your pool cover quickly and they are too expensive to risk that. I normally leave mine off for at least 4 hours before I put it back on.
Pool Care Handbook and Video Course
When I bought my house with a swimming pool, I knew absolutely nothing about pool care. I just winged it for a while, making many mistakes along the way.
Fortunately, I was recommended Swim University’s Pool Care Handbook and Video Course. I bought it and it was an absolute game-changer.
It was the best money I spent that year. I learned everything from basic cleaning to advanced troubleshooting. Swim University offers a no-quibble refund policy too so what do you have to lose?
Also read: How to keep a pool clean without a pump
I have had hot tubs for over 20 years and a pool for the last 10 years. I had to learn how to clean, maintain and fix them the hard way. Since then I have helped many friends and neighbors with their pools and now I want to share everything I have learned with you. About Me