When pools are closed until the next warm weather season, the water is not filtered and chemicals are not added. During this time, the water turns green with algae and debris may enter the pool. If the pool was not covered at the close of the previous season, the condition of the water will be much worse. Pool opening requires much patience on the part of the homeowner to restore the green water to its former crystal clear condition. When to open a pool varies depending on the climate, but the end of May usually is a good time.
Drain the water and remove the debris that has accumulated on top of the pool cover. Pull the cover back, wash and dry it, and then store it for the summer.
Inspect the pool filter and pump to ensure they are in good condition, and replace any damaged or malfunctioning parts.
Change the filtering material, usually a type of filter sand, if needed.
Fill the pool with water to the appropriate level above the skimmer basket.
Scoop out large debris, such as leaves, from the pool water with a large leaf net. Continue scooping until no more debris comes up in the net.
Turn on the filter and let it run 24 hours a day for several days or until the water is clear. Backwash the filter several times a day to clean the filtering material.
Test a sample of water to determine the pH and alkalinity levels. Add pH reducing, pH decreasing or alkalinity increasing chemicals to adjust these levels.
Add an algaecide chemical to the pool, following the directions on the bottle for the appropriate amount to add for the size of your pool.
Shock the pool with a super chlorinating liquid or powder chemical over a period of several days to make the green water clear. Start with about three gallons of liquid shock or follow the package directions. The total amount of shock to use is up to you, but the pool will clear faster when more shock is added.
Scrub the sides of the pool with a brush at least once a day to remove the algae and prevent algae from settling on the sides. Brushing also helps to stir settled algae into the water so it can be run through the filter.
Vacuum remaining debris from the bottom of the pool when the water is clear enough to see the debris. Hiring a professional to power vacuum the pool may be the best choice for large amounts of debris because this saves wear on the pool's filter.