A pool turns green because free chlorine ran low long enough for algae to bloom. Clearing it takes a sequence rather than one dose: balance, shock, brush, filter around the clock, and repeat.
Starting the sequence today matters because a green pool isn’t safe to swim in, and the darker it gets, the longer the recovery takes. In a Plano summer the bloom can take water that was clear last week to pea soup in a day or two.
Why pools turn green so fast in North Texas
Algae spores land in your pool constantly, on the wind, on swimsuits and toys, and with rain, and they stay invisible as long as your chlorine is doing its job. The moment chlorine drops below the level it needs to hold, those spores multiply, and in our climate they multiply fast.
The CDC recommends keeping free chlorine at a minimum of 1 ppm, or at least 2 ppm in a stabilized pool, which is most pools here. Its guidance warns that chlorine “must be routinely tested, as many things can reduce its concentration,” and it names sunlight among them. That margin disappears fastest here, because three things make North Texas especially friendly to algae:
- Heat. Algae thrives in warm water. Our pools sit in the 80s and 90s for months, which is prime growing temperature.
- Sunlight. Long, intense summer sun burns chlorine out of the water quickly and feeds algae through photosynthesis at the same time.
- Rain and storms. A summer downpour dilutes your chlorine, drops organic debris in the water, and shifts the chemistry, often right before a bloom.
The classic Plano scenario is a hot week plus a missed chemical check or a storm. If you’re in the middle of a run of triple-digit days right now, our guide to pool care through a Texas heat wave covers what to change in the routine before it gets to this point.
Do not swim in a green pool
Green water means the sanitizer is depleted, which often means bacteria are present alongside the algae. Reduced visibility is also a real drowning hazard, especially for kids. Keep everyone out until the water is clear and the chemistry is back in range.
Reading the shade of green
How green the water is tells you roughly how much work it will take to recover. We use the same scale to quote a recovery clean:
| What you see | What it means | Effort to clear |
|---|---|---|
| Slightly cloudy, faint green tint | Early bloom, chlorine ran low | Often clears in 1 to 2 days |
| Light green, floor still visible | Established algae bloom | 2 to 3 days of shock and filtering |
| Solid green, steps not visible | Heavy bloom | 4 to 6 days, usually more than one shock round |
| Dark green or black, surface film | Severe, possibly with debris and stains | 7 to 10 days, and the point a drain gets considered |
The green-to-clean recovery, step by step
The green-to-clean recovery is six steps, and the order matters. Skipping a step is the most common reason a pool goes cloudy gray and stalls instead of clearing.
Step 1: Clear out the debris
Skim off as much surface debris as you can and empty the skimmer and pump baskets. The cleaner you start, the less organic material is fighting your chlorine.
Step 2: Test and balance the basics
Test your water and get the pH into range, around 7.4 to 7.6. Chlorine works better at the right pH, so this small step makes every dose of shock that follows do more. If you aren’t sure what your numbers should be, our pool water chemistry guide lays out every target level.
Step 3: Shock the pool, hard
Shocking means raising chlorine high enough to kill the algae and oxidize the organic load. A light bloom might clear with a single strong shock, but a deep green pool usually needs a larger dose and often more than one round. This is the step people underdose most.
Step 4: Brush every surface
Right after shocking, brush the walls, steps, floor, and any corners where algae clings. Brushing breaks up the colonies so the chlorine can reach them and so the dead algae lifts off the surfaces into the water where the filter can grab it.
Step 5: Run the filter around the clock
Continuous filtration is the step that clears the water, and the one homeowners cut short. Run the pump 24 hours a day until the water clears, and backwash or clean the filter as the pressure climbs, because a clogged filter stops removing the dead algae.
Step 6: Repeat and then vacuum
Re-test, re-shock if the water is still holding green, and keep brushing. As the algae dies it settles to the bottom as a gray or tan dust. Vacuum that out, ideally to waste if your system allows it, so it doesn’t recirculate.
The cloudy-blue stage is good news
Green water usually passes through a cloudy, milky-blue stage on its way to clear. The cloudiness is dead algae suspended in the water and waiting to be filtered out, so it’s progress rather than a setback. Keep that filter running and it will polish out. Patience at this stage beats dumping in more chemicals.
How long it takes
Once treatment is right, a typical Plano pool clears in the times the shade table gives. Light green takes 2 to 3 days and solid green 4 to 6. Dark green takes 7 to 10, the point where a drain and refill or acid wash can be the faster, cheaper path. They are the same ranges as our stage-by-stage recovery log, which publishes the reading that closes each stage rather than the day on a calendar.
The point to stop is when the water isn’t moving through those stages. If you have held a shock level for two full days, brushed, and filtered continuously, and the pool is still the same green it was on day one, something is holding your chlorine down rather than the algae winning. Most often that is cyanuric acid (CYA), sold as stabilizer, sitting high enough that the chlorine you’re adding can’t reach an effective level at any realistic dose. Get a full panel run, including CYA, before you buy another case of shock. Adding more chlorine to a pool that can’t use it is the most expensive way to make no progress.
A full drain isn’t a DIY shortcut in North Texas
If someone suggests emptying the pool to deal with a swamp, understand what that involves here. Our expansive clay holds groundwater that pushes up on an empty shell, which can lift or crack it, and exposed plaster dries and crazes fast in summer heat. A full drain is sometimes the right call on a severe pool, but it’s a job for someone who will check the hydrostatic relief valve first and refill immediately, not a Saturday project. Partial exchange, staged over a few days, is the safe version and usually enough.
Keeping it from happening again
Three habits prevent most blooms:
- Hold your chlorine steady. The pools that turn green are usually the ones that ran low on chlorine for a few days.
- Keep CYA in range. Too little and the sun burns your chlorine off by noon. Too much and you have to hold chlorine so high to keep it effective that the level becomes impractical, and algae slips in through the gap. Both ends of that range end in the same place.
- Check the pool weekly, especially after storms. A summer storm is the most common trigger for a bloom. A quick test and a small chlorine bump afterward heads it off.
A week is about the longest a pool can coast in our heat before chemistry drifts far enough to invite algae back, which is why most North Texas pools do best on weekly service through the summer.
Know the number before anybody quotes you. Green pool recovery is priced by condition rather than by the hour, and published DFW prices run from a couple of hundred dollars for chemicals and filter time to well over a thousand where a drain is involved. What a green pool cleanup costs in DFW works through the four things that decide which end your pool lands on, three of which you can see from the deck.
Staring at a green pool right now?
If you would rather not spend your week mixing chemicals and babysitting the filter, this is one of the most common calls we get. We bring the pool back to swim-ready with a condition-priced green-to-clean recovery, then keep it that way. Reach out through our contact form or call and we’ll get you on the schedule.
