Green water is the most common pool problem we hear about. In most cases it is algae, and algae grows when sanitizer runs low, circulation is poor or the water warms up quickly. The good news is that it is fixable.
Common causes
- Low chlorine. Heat, sunlight, heavy use and rain all use up chlorine. If it drops to zero, algae can take over in a day or two.
- High pH. Chlorine works much less effectively when pH is high, even if the chlorine reading looks fine.
- Low stabilizer in an outdoor pool, so sunlight burns chlorine off quickly.
- Poor circulation or filtration: short pump run times, a dirty filter or dead spots in the pool.
- Metals. Copper or iron, sometimes from fill water or corroding equipment, can turn water green, especially after shocking. Metal-related green tends to look clear rather than cloudy.
How to clear a green pool
- Test the water. Bring a sample to a pool store if you can. Poolmaster offers in-store testing at 1875 Leslie St.
- Balance the pH into the normal range so chlorine can do its job.
- Brush everything to break up algae on walls, steps and the floor.
- Shock the pool at the dose the label gives for algae, and keep chlorine elevated until the water clears.
- Run the filter continuously, and clean or backwash it often. It will clog quickly.
- Vacuum dead algae once it settles. Vacuuming to waste can help if your system allows it.
Badly neglected pools, where you can’t see the floor, may take several days and more than one treatment.
Keeping it from coming back
- Test at least weekly, and more often in hot weather.
- Keep chlorine and pH in range, and shock after heavy use.
- Run the pump long enough to turn the water over every day.
- Use an algaecide as a preventive if you are prone to blooms.
If you would rather hand the job over, our weekly service keeps your chemistry on track all season.
Pool turned green? Request a quote or call 416-449-1450.
