When/Why do I need fresh water in my pool? There are circumstance where replacing the pool water is necessary to reduce the buildup of certain chemicals. These chemicals can include calcium, metals, cyanuric acid(stabilizer) and total dissolved solids. The easiest way to remedy the situation is to partially drain the pool and refill with fresh water. It has been suggested that draining and refilling a pool before the swimming season is beneficial in keeping these substances at a happy medium. If you have any questions about your pool chemistry, contact The Pool Man Inc, your Houston Pool Builder, and we would be happy to help you.