Can household bleach be used to increase the free chlorine levels in a pool?

The answer is yes. To maintain a safe bacterial count in a swimming pool you need to have a free chlorine value of around 1.2 parts per million. Household bleach can achieve this at the correct dosing rate. The dosing rate will vary dependant on the concentration of the bleach. Typically household bleach can have a sodium hypochlorite concentration of between 3 and 6% when manufactured. Dependant on storage conditions and age this figure can alter as well. Best practice is to use a free chlorine tester to measure the chlorine in the pool and dose accordingly. The downside of using houshold bleach is that continued dosing can raise the pH level of the pool which reduces the effectiveness of the chlorine. In this case it is necessary to add an acid (usually hydrochloric acid) to keep the pH value between 7.2 and 7.4. CAUTION never mix household bleach directly with acids as it will release large quantities of toxic chlorine gas.

+++

Household bleach usually uses calcium hypochlorite as its active ingredient, as do most chlorine-donor swimming-pool disinfectants, but I would NOT recommend bleach for two reasons.

1) It may not be a simple hypochlorite solution in water, but may contain additives such as surfactants and perfumes.

2) It's extravagant! You buy bleach as a solution of chlorine-donor in water. Although granular Calcium Hypochorite sold for Swimming Pools contains a binder, it is far more concentrated - typically 60% - so far more economical than the bleach. You'd need many gallons of the household cleaner to give your pool the Cl level it needs! Also of course, bleach contains no stabiliser against UV degradation - you can buy pool disinfectant with this already in the compound.