Fresh Water: Drain the water in the pool.

Every four to five years, the draining of the pool water is good to help maintain the proper chemical balance. Through the years, hard particles stay in the water, they don't evaporate, so draining is the option. A chlorine wash may be necessary if algae is a problem. Do not mix the chlorine and the acid for that makes a lethal gas. Rubbing stubborn algae spots and using chlorine can brighten the surface of the plaster. It is not like an acid wash, where a thin layer of plaster is removed, but prepares the pool for fresh water. After the water has been replaced, adding conditioner(cyanuric acid) helps to hold the chemicals in the water so they can do the work set out for them. The pool is now ready for everyone to enjoy.