Shocking a pool during the daytime can be ineffective or even dangerous due to the effects of sunlight on pool chemicals. Shocking is the process of adding extra chlorine or other sanitizers to a pool to kill algae, bacteria, and remove contaminants. There are a few key reasons why it’s best to avoid shocking your pool in direct sunlight:
Sunlight burns off chlorine
One of the main issues with daytime shocking is that sunlight rapidly dissipates chlorine and bromine – the two most common pool sanitizers. The UV rays in sunlight essentially “burn off” and use up the chlorine before it has time to work properly. This means the shock treatment you just added can become ineffective very quickly.
Chlorine and bromine work best when they are able to sit in the pool water for an extended period of time. Shocking at night allows these chemicals to work overnight without being diminished by the sun. The chlorine has time to kill contaminants and algae spores before the sun returns in the morning.
Risk of forming chloramines
Shocking during the day can also lead to the formation of chloramines – irritating compounds formed when chlorine binds to nitrogen-containing contaminants like urine, sweat, and dirt. Chloramines can cause red eyes, itchy skin, and breathing irritation for swimmers.
When you shock a pool, the chlorine levels temporarily become very high as the shock chemicals dissolve. If this happens while the sun is still out, the chlorine can quickly bind to contaminants in the water before killing them off fully. Not only are chloramines bad for swimmers, they are also less effective at sanitizing than free chlorine.
By shocking at night, you avoid this issue. The high chlorine levels can dissipate by morning, leaving you with bacteria-free water instead of irritating chloramines.
Safety concerns
Performing maintenance while swimming is occurring raises some potential safety issues. Firstly, the high chlorine levels immediately after shocking can irritate eyes, skin, and lungs if swimmers don’t exit the pool in time. Secondly, having equipment, chemicals, and containers around the pool’s edge during the day presents a physical hazard.
For these reasons, it’s generally advised to perform pool shocking at night when no one is swimming. This ensures proper chlorine dissipation and no safety risks from temporary high chemical levels.
How to shock a pool properly
To effectively shock your pool, follow these steps:
- Test the chlorine level using test strips. Ideal is 1-3ppm.
- In the evening after swimming has ceased, add shock per the product instructions.
- Run the filter pump for proper water circulation.
- Test chlorine levels the following day before swimming resumes.
- Add chlorine tablets or liquid as needed to maintain proper levels.
Granular dichlor shock is recommended for occasional shocks. Add it directly to the pool water while running the pump. For weekly maintenance shocking, liquid or tablet shock products are easier to handle and dose.
Aim to shock once a week or more often if chlorine drops below 1ppm or algae start forming. Shocking works best if done consistently rather than just occasionally.
The science behind pool shocking
On a chemical level, pool shock helps sanitize pool water by:
- Oxidizing contaminants and organic matter – Chlorine destroys bacteria, viruses, algae spores, urine, sweat and other contaminants by oxidation. It rips apart chemical bonds in organics, leaving only harmless byproducts like chloride, nitrogen, and water.
- Providing high levels of free chlorine – Free chlorine is the most effective sanitizing form. Pool shock brings chlorine levels up to 5-10ppm temporarily to kill germs and algae already in the water.
- Activating bromine – Sodium bromide shock converts inactive bromide into active hypobromous acid, which sanitizes the water. Bromine also remains active longer than chlorine.
Together, these chemical effects provide a deep clean and reset for pool water quality. While chlorine and bromine tablets maintain a daily sanitizer residual, periodic shocking ensures contamination is fully eliminated.
Choosing the best pool shock
There are a few different pool shock products to choose from. Each has pros and cons.
Chlorine Shock
- Granulated Dichlor – This fast-dissolving shock is ideal for giving pools an occasional heavy shock. Dichlor (sodium dichloroisocyanurate) provides a high dose of chlorine.
- Liquid chlorine – Available in concentrated form, liquid chlorine offers a convenient way to regularly shock the pool. It does not last as long as dichlor.
- Chlorine tablets – Tablet chlorine can also be used for weekly shocking. They dissolve more slowly than other forms which prolongs sanitizing effects.
Non-Chlorine Shock
- Potassium monopersulfate – Sold as Oxy-Boost, this chemical-free oxidizer shock is a good chlorine-alternative. It works well but does not provide a sanitizer residual.
- Sodium bromide – Activated by oxidation, sodium bromide forms hypobromous acid to sanitize pool water without chlorine’s downsides.
While chlorine is the most popular and economical option, non-chlorine shock can be easier on sensitive skin and Outdoor Or Inground Pools . Bromine shock provides a more stable long-term residual than standard chlorine shock.
Dealing with high chlorine after shocking
It’s normal for pool chlorine levels to measure high immediately after shocking. Here’s what to do:
- Re-test chlorine after 2-4 hours allowing levels to drop.
- Do not swim until chlorine is below 5ppm – irritation can occur above this point.
- Run the pump and let the pool circulate to dilute the chlorine.
- If levels remain too high after 24 hours, partially drain and refill the pool water to dilute.
High chlorine levels dissipate faster in sunlight. But it’s still best to wait until chlorine is at a safe swimming range before using the pool again.
Common pool shocking mistakes
While seemingly simple, shocking a pool incorrectly can reduce effectiveness and create issues. Things to avoid include:
- Not shocking enough – Under-dosing will fail to fully clean the water.
- Overshocking – Too much can lead to very high chlorine for an uncomfortable swim.
- Relying only on chlorine tablets – Tablets maintain a base residual but shocking provides deeper sanitization.
- Pouring shock chemicals in the wrong spots – Add directly into pool water for proper mixing.
- Shocking in sunlight – UV rays rapidly burn off chlorine before it works.
- Letting free chlorine drop too low – Below 1 ppm can’t kill germs or algae effectively.
Test water chemistry regularly and shock as soon as chlorine falls below ideal 1-3ppm level. With routine shocking, you’ll maintain clean, safe water all season long.
FAQs about Shocking Pools
Can I shock my pool in the rain?
Shocking the pool in the rain is not recommended. Rainwater dilutes the chlorine, making the shock treatment less effective. It’s best to wait for dry weather before shocking your pool.
How soon can I get in after shocking?
You should wait at least 24 hours before swimming after shocking to allow chlorine levels to stabilize and drop back to safe levels under 5 ppm. Test the chlorine and pH to ensure proper water balance for swimming.
Should I shock at night or day?
Shocking at night, after the sun has set, is best. The sun’s UV rays burn off chlorine so shocking is less effective during daylight. Overnight also allows time for the chlorine to work before swimmers enter again.
How often should you shock a pool?
For maintenance, shocking the pool weekly is typically recommended. But shocking more frequently may be needed if chlorine is below 1 ppm, when it rains a lot, or if algae start forming.
What happens if you don’t shock your pool?
Without periodic shocking, chlorine levels will remain low. This allows germs, bacteria and algae to grow, creating an unsafe, unsanitary swimming environment. Consistent shocking removes contaminants and keeps water clean.
Conclusion
Shocking your pool is an essential part of proper water maintenance. By oxidizing contaminants, boosting sanitizer levels, and burning off organics, it keeps water safe and pleasant for swimming. However, shocking during daylight is ineffective and can even create issues like skin irritation. For best results, rely on overnight shocking once a week or as needed. Test water frequently, allow time for chlorine dissipation, and you’ll have a sparkling clean pool all season long.