You might have an infestation of algae, fungus or bacteria that can deplete normal chlorine levels and it is possible for this to occur without many visible signs. Your pool may appear to have a dusty look on the pool bottom. If you brush it and it clouds the water, then it is most likely a Mustard Algae.
Despite how it sounds shocking a pool has nothing to do with electricity or with revealing something completely unexpected. Shocking is the process of adding chemicals (usually chlorine) to your pool to: break apart chloramines, also known as combined chlorine. quickly raise your chlorine level.
The Bottom Line about Pools and Chlorine
As mentioned above, you could probably swim in a pool without chlorine without any major health issues. However, long-term use of a pool lacking chlorinated H2O could make you sick or, at the very least, contribute to rashes and other types of skin irritation.
If you test your pool water and can't get a chlorine level reading at all it may be due to a very high chlorine demand. A high chlorine demand is the inability to keep an adequate level of chlorine in the pool water even though the water appears to be balanced and properly maintained.
The goal of shocking your pool is to raise the free chlorine level of your pool water to roughly 10 times the combined chlorine level of your pool water.
Shock is liquid or granular chlorine. You should add one gallon (or one pound) of shock per 10,000 gallons of pool water every week to two weeks. During hot weather or frequent use, you may need to shock more frequently.
Aim to maintain a chlorine level of 3 to 5mg/l at all times. How frequently you add more chlorine will depend on your usage and bathing habits. It could be daily, every two to three days or weekly. For 1mg/l, add 2g per 1000 litres.
How Often Should I Shock My Pool? Shocking your pool regularly will help to keep the water clean and free of contaminants. You should aim to shock your pool about once a week, with the additional shock after heavy use. Some tell-tale signs that your pool needs to be shocked are cloudy, foamy, green, or odourous water.
Sun Down – You'll want to shock your pool in the evening when the sun has gone down. This gives your pool plenty of time during the night to free the chlorine and clean the water. In the morning, you should be able to enjoy your pool. If you shock your pool during the day, the sun's UV rays will dissolve the chlorine.
Can you put too much shock in a pool? SKIMMER NOTES: It's unlikely but it could happen. It would take a lot of shock to really make the water unsafe for swimming. The best way to make sure you're safe to swim is to test your pool water and make sure free chlorine levels are between 1-4ppm for healthy swimming.
A pool filter should be run for a minimum of 6 hours after shocking a swimming pool. This is to allow the filter to clean the water and give the shock enough time to fully mix with the pool water. Running the filter after shocking for 24 hours to 7 days is necessary if the pool has a large amount of algae.
SKIMMER NOTES: No. Chlorine and shock are not the same thing.
Shock has a more intense chemical strength than the traditional chlorine sanitizers, and it also differs in how you should apply it to your swimming pool. Short answer: No. Chlorine sanitizers and shock are similar but different in strength.
It Should Not Be Done Together
This is because when you mix chlorine and algaecide together, it renders both of them useless. Hence, you should first shock the pool and wait for the chlorine levels to fall below 5 PPM.
The benefit of chlorine tablets is that the tablets slowly dissolve over time so therefore you have a supply of chlorine entering the water over a period. Chlorine granules however must be added so there is a higher risk that levels may drop if the hot tub is not attended to, adding risk of bacteria growth.
After Shocking Your Pool
It is safe to swim once your chlorine levels are around 5 ppm or after 24 hours. It is always best to test first!
Never close the cover immediately after shocking the pool. It is recommended to wait several hours before closing the cover. Use a test kit to regularly test the pool water. If the tests results are good, this does not imply the water chemistry was good prior to your current test results.
Before you start pouring shock in the pool, the first step is to brush the sides and floor of your pool to loosen all the algae. Doing this breaks the skin and allows the pool shock to more easily kill the algae. Once you've done this, it is important to make sure you have the proper pH level in your water.
It's always best to run the pool pump during the hottest times of the day. The sun is one of the causes of chlorine depletion in your pool. The water moving around helps protect the chlorine from being burnt out from the sun.
Algae will remain in your pool after shock if you've had insufficient chlorine and an overabundance of metal elements in the pool water. Therefore, to start the cleaning process. Remove all the debris from the pool with a leaf net and then let the smaller dirt fragments settle.
Liquid chlorine and granular shock have the same active chemical that sanitizes your pool, what changes is the strength and the way you use it. Liquid chlorine is less costly, unstabilized and comes in liquid form. Granular shock is stabilized and comes in a solid form that dissolves in your pool.
High doses of chlorine, like pool shock, can cause temporary cloudiness as it kills contaminants. High levels of pH, alkalinity, and calcium hardness are more likely to cause cloudy water.
Best Time to Shock Your Pool
The best time of day to shock pool is when the sun is down. So, experts recommend shocking your pool in the evening or at night, to make sure it does its job. Shocking during the day can be ineffective as UV rays from direct sunlight significantly reduce free chlorine levels.
After you have cleaned the pool of all debris it is best to shock in the evening because the sun's UV rays will dissolve the chlorine too quickly before it has a chance to attach and oxidize.
It is recommended that chlorine be added at the end of the day once the sun has set and there are no more bathers in the pool.