Why Pools Turn Green in Texas — and How to Get It Clear

A green pool looks alarming, but it’s one of the most common — and most fixable — problems we see around Cypress and Katy. Here’s why it happens in the Texas heat, what the color is actually telling you, and how to get your water clear again.

What turns a pool green?

In almost every case, green water is algae. Algae is always in the air and washing into your pool; the only thing keeping it from taking over is a steady level of chlorine. The moment free chlorine drops below what’s needed to kill it, algae blooms — and on the Gulf Coast, it blooms fast. In a Cypress or Katy summer, a perfectly clear pool can go cloudy in 24–48 hours and fully green within a few days.

The usual triggers we see:

• The pump isn’t running long enough. Water that doesn’t circulate can’t stay sanitized.
• A dirty or clogged filter. If it can’t filter, the chemicals can’t keep up.
• Heavy Texas rain. A big storm dilutes your chemistry and drops chlorine overnight.
• A missed week or two. Vacation, a lapsed service, or just a busy stretch in July.
• A broken chlorinator or salt cell. If it stopped feeding chlorine, you may not notice until the water turns.

What the color is telling you

How green it is roughly tells you how much work it’ll take:

• Light green or cloudy: an early bloom. Usually the fastest to reverse.
• Full green, can’t see the bottom: an established bloom that needs shocking, continuous filtration, and brushing over several days.
• Dark green, swampy, or black spots: heavy algae — sometimes black algae rooted in the plaster. This is the longest to clear and the one where a pro really matters.

How a green pool actually gets cleared

Clearing green water isn’t one big dump of chemicals — it’s a sequence:

1. Test and assess first. A green pool with a dead pump is a completely different job than one with a clogged filter. We look at the equipment before we touch the water.
2. Balance, then shock. We correct pH and alkalinity so the shock can actually work, then shock to a level that kills the bloom — not just tints it.
3. Filter and brush. The pump runs continuously while we brush the walls and floor, and we clean or backwash the filter as it pulls the dead algae out.
4. Repeat until clear. Most pools go from green to clear in a few days to about a week, depending on how far gone they were.

Can you fix a green pool yourself?

If it’s only light green, sometimes yes: get the pump running, clean the filter, balance the water, shock in the evening, and brush daily while you run the filter. Be patient — it clears over days, not hours.

Where we’d tell you to call a pro: if it’s dark or swampy, if it keeps coming back after you clear it (that usually points to an equipment or circulation problem), or if you’ve got a heater and automation you’d rather not damage guessing at chemistry. We always look and quote before we touch anything — you’ll never get a sight-unseen price from us.

Keeping it from turning green again

Once it’s clear, staying clear comes down to consistency: run the pump enough for the season (more in the summer heat), keep chlorine steady, clean the filter, and — the big one — don’t skip weeks in July and August. The single most reliable way to never see green water again is steady weekly service from someone who catches a problem before it becomes a bloom.