Levels

• In order to maintain a properly disinfected pool, its available chlorine should be approximately 2.0 parts per million (PPM), which is the recommended level. As well, proper pH balance needs to be between 7.0 and 8.0. Outside that range, and chlorine performs poorly, or it may even be nonexistent. That's why it's important to check chlorine and pH levels on a regular basis. Under normal conditions, once or twice a day should suffice.
  
  

Wait Time

• Often, chlorine will need to be added to bring levels up to 2.0 PPM. The typical formulation of this chemical is granulated calcium hypochlorite. For this specific type, approximately 1 pound per 10,000 gallons of pool water is required in order to maintain chlorine at that level. How long it will need to set, or "wait," depends on how low the levels are. If they're very low, it might take 45 minutes or more.
  
  

Disinfection

• On occasion, you may be confronted with a seriously contaminated pool. This could be after a strong and sustained rainfall or after high numbers of swimmers have been in the pool. It could even be after the pool has been contaminated by fecal or other organic material. These are all occasions when a pool may require superchlorination, or shocking. Fortunately, unless the pool is completely overwhelmed, chlorine is effective in from one to 45 minutes.
  
  

Shocking

• Shocking a pool means adding more chlorine than normal to raise its levels above 2 PPM. Sometimes, this could mean significantly above that figure, perhaps double or even triple that amount. That's because the water's in such dire straits, either from organic contamination or because it's been overwhelmed by algae, that regular dosing with chlorine is ineffective. Wait time varies, but doing so after sunset and then waiting overnight before using the pool is typically the best method.
  
  

Considerations

• Before adding pH balancers, you should always make sure your pool chlorine is stabilized. That's because most commercial chlorines will raise pH somewhat all on their own. Once you've waited, either one to 45 minutes or overnight, and chlorine levels are stable, check your pH and adjust as required to bring it to between 7.0 and 8.0; 7.2 to 7.4 is best. Direct sunlight also dissipates chlorine, meaning lots of it might necessitate frequent chlorination.