Bleach is the sodium hypochlorite version of chlorine. The most common type of pool chlorine, though, is calcium hypochlorite. For swimming pools, it's typically used in solid form, as a powder or in sticks or tablets. Its actual chlorine content is around 65 percent, while bleach averages approximately 5 percent. More of it is needed to achieve the same effect as calcium hypochlorite. However, it's far less expensive --- and it is just chlorine, after all.
As long as liquid bleach is handled according to instructions, it's safe for use as a pool disinfectant. The same goes for standard calcium hypchlorite chlorine, too, so treat either chemical with respect. Most often, because bleach is relatively weaker compared to "regular" pool chlorine, it's also added directly to the pool skimmer. That's so it can be distributed throughout the pool by the pool's filter. Avoid splashing any type of chlorine onto your skin and the eyes.
In order to keep a pool at the recommended chlorine level of 2 parts per million (PPM), the right amount of chlorine needs to be added. For calcium hypochlorite, that means about 3/4 lb. per 10,000 gallons of water. Liquid bleach requires 1 gallon per the same amount of water. If you have a 30,000-gallon pool, for example, you'll need about 3 gallons of bleach to take your pool from 0 PPM up to 2 PPM.
As of May 2011, a 25-pound bucket of calcium hypochlorite costs nearly $90. A gallon of liquid bleach averages about $2, meaning the equivalent amount of bleach will only cost $50. However, it's not necessary to buy 25 gallon-size bottles all at once. That's because it won't be necessary to add a whole gallon regularly to keep chlorine levels stabilized at 2 PPM. Measure your pool's chlorine level with a pool test kit and then add bleach as needed.
Chlorine in a pool also needs to be stabilized, no matter whether it's in bleach or standard forms. That means you'll need some sort of stabilizer to prevent chlorine from being dissipated by sunlight. The most common stabilizer on the market is cyanuric acid (CA), which is only sold through swimming pool supply outlets. Also, it's important that pool pH levels be between 7 and 8 in order for any type of chlorine to be effective.