How to Shock a Pool

Shocking your pool kills bacteria and removes contaminants that make your pool water cloudy. Adding chlorine to your pool is a good way to keep it clean on an everyday basis, but you still need to shock your pool regularly to remove dead chlorine and keep the water clear.


Why Shock Your Pool?

Before you learn how to shock a pool, it's important to understand why it is necessary. Between shock treatments, chlorine in your pool water attaches to bacteria and other contaminants in your pool, forming a molecule called a chloramine. Once a chlorine molecule has become part of a chloramine, it's no longer useful -- which is why it's called "dead chlorine." Too much dead chlorine can make pool water cloudy, so you need to remove it regularly by shocking your pool.


Pool Shock Chemicals

There are four types of chemicals you can use to shock your pool. Each type has its own advantages and disadvantages that you should consider as you make your decision.


Calcium Hypochlorite

The most popular pool shock chemical is calcium hypochlorite. It's less expensive than most other types of pool shock, which could explain its popularity. You need to prepare calcium hypochlorite by dissolving one pound of chemical in five gallons of water before you add it to the pool.


Lithium Hypochlorite

If you live in an area where the amount of calcium in the water is very high, you may prefer to use lithium hypochlorite. Too much calcium can make pool water cloudy or cause scale to form on the sides of the pool. There's no need to dissolve lithium hypochlorite in water before you add it to your pool; you can simply pour it in.


Granular Chlorine

You can use granular chlorine both to shock your pool and as a regular chlorine treatment. Use small doses of this chemical to bring your pool chlorine up to the appropriate level or add a large dose to shock your pool. There is no need to dissolve granular chlorine before adding it to the pool.


Non-Chlorine Shock

If you use bromine rather than chlorine to keep your pool clean, then you need to use a non-chlorine shock, such as potassium peroxymonosulfate. Chlorine pool owners can also use this chemical to shock their pools. The advantage of non-chlorine shock is that you have to wait only 15 minutes to swim in the pool whereas chlorine pool shocks require you to wait at least eight hours. The downside is that this chemical is very expensive.


How to Shock a Swimming Pool

It's usually best to shock your pool after the sun has set, so that the UV rays from the sun don't affect the chemicals. Begin by preparing your pool shock chemicals according to the packet instructions. If you need to pre-dissolve your pool chemicals, stir the solution thoroughly to make sure it is well mixed. Turn on the pool filtration system and then pour your pool chemicals into the pool water close to a return line fitting. Leave the pool for the required amount of time (usually eight hours) and then measure the chlorine levels in the water. If the level is higher than 3ppm, the pool isn't yet ready for swimming.


How Often Should I Shock My Pool?

Pool experts recommend shocking a pool at least once a month. Warmer pools may need more frequent shocking. To determine whether your pool needs shocking, use a test kit to measure the levels of free and total chlorine. If the total chlorine level is more than 2ppm greater than the level of free chlorine, you need to shock your pool.


The "Shocking" Conclusion

Shocking your pool regularly keeps the water clean and clear. Test your pool at least once a week to see whether the water needs shocking. Remember to follow the dosing directions for your pool shock chemicals and wait until your chlorine levels return to normal before swimming.
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