There are benefits and disadvantages to having a salt water pool. You need to drain the pool less frequently than if you were manually chlorinating a pool, but salt water is considered a contaminant by the EPA and you have to follow specific guidelines for sending it down drains. You need to drain your pool if salinity levels rise above 6,000 ppm (parts per million).
Benefits Of Salt Water
With a salt water pool, you can enjoy the softer and smoother feel of the water, plus you don't have to spend money on chlorine or shock. The water does not smell like chlorine and naturally rejects algae growth. Since there are no harsh chemicals, common irritations like red eye and swimmer's ear are nearly eliminated. Since the stabilizer levels are controlled with salt water systems, you can avoid draining the pool as frequently.
You do need to check with your local government regarding draining procedures. For example, you may need a permit and also information on where to dispose of the water. Because the water is not chlorinated you can often let the water drain into a sewer clean-out or stormwater retention basin.
You definitely need to drain some water from the pool when salinity reaches a 6,000 ppm level. Most salt water pools should be maintained with a salinity level of 2,500-4,000 ppm. The amount you drain depends on how elevated salinity levels are. You can rebalance the salinity level by diluting the pool with new fresh water. Some pool equipment and concrete can be corroded and damaged by high salinity levels, so keep the levels at the rate suggested in the owner's manuals for these pieces of equipment.