Summer algae prevention when the water is ninety degrees

Why do pools go green in August and not in May?

Because chlorine consumption rises with temperature and sunlight and algae growth rises with them too. Water at seventy five degrees holds a chlorine reading through a day comfortably. Water above ninety burns through the same dose within a day, sometimes less, and every hour of that afternoon is an hour of algae doubling.

What did not change is the owner routine. The Saturday dose, the six hour pump schedule and the once a week test that worked perfectly in May are simply not enough water treatment for August, and the pool is not being neglected so much as under fed.

The tell is a chlorine reading that is fine on Sunday morning and zero on Wednesday evening. That is not a leak in your chemistry, it is demand. The fix is more chlorine more often, not a different brand of chlorine.

What should change on the equipment side?

Run time first. Whatever your pump runs in April, add hours in July. A pool needs at least one full turnover a day in mild weather and closer to two when the water is hot, the sun is direct and people are actually swimming.

Salt pools need the same conversation in a different form. A cell only produces chlorine while the pump runs, so a salt pool on a short summer schedule literally cannot make enough. Raise the run hours before you raise the output percentage, because longer and gentler is easier on the cell.

Filter cleanliness matters more in summer than any other time. Swimmer load, sunscreen, oils and heat all peak together, and a loaded filter turns a manageable week into a hazy one. Check the pressure against your clean baseline every couple of weeks in season rather than every couple of months.

And check the return eyes. A pool that circulates well is a pool where chlorine actually reaches the shady corner. Aim them to rotate the whole body of water rather than to make a pretty ripple.

What should change on the chemistry side?

Get stabilizer into the middle of its range before summer, not during it. Too low and your chlorine evaporates in the sun. Too high and every chlorine reading is worth less than it looks. Late spring is when to fix that number, because fixing it in August means a water exchange during peak evaporation.

Raise your free chlorine target rather than your dose size. A pool that ran 3 ppm comfortably in April may need to hold closer to the top of its appropriate range in August. Holding a level is what prevents algae. A big Saturday dose that is gone by Monday does not.

Watch pH more closely. Aeration, heat and high bather load all push it around, and a pool drifting to 8.0 has quietly weakened its own chlorine at the worst time of year.

And shock after events rather than on a schedule. A pool party, a storm, a week of heavy use, a dog in the pool. Those are the moments that justify a real shock, and doing it that evening rather than the following Saturday is what keeps the water ahead.

What are the habits that actually keep pools clear?

Brush weekly, and brush the places you do not look at. Steps, the shaded wall, behind the ladder, under the tanning ledge lip, the corner the return does not reach. Algae starts in those spots every time, and thirty seconds of brushing each is the entire prevention.

Test twice a week in season. Free chlorine and pH. It takes three minutes with a drop kit and it catches a downward trend before it becomes a bloom.

Net the surface before things sink. Everything organic that reaches the floor is chlorine demand plus phosphate later.

And dose in the evening. Chlorine added at eight at night gets a full night of work before the sun touches it. The same amount added at noon in July is partly gone before it reaches the far end of the pool.