The scenario is always the same. You leave for two weeks. The pool sitter forgets. You come back to what looks less like a pool and more like a pond. Panic sets in. Draining and refilling in Orange County isn’t cheap, and it can crack an empty pool if not done right.
Good news: most green pools can be recovered without ever pulling the plug. Here’s how we do it.
Day 0: Assess Before Acting
Not every green pool is the same. There are three flavors:
- Light green — early algae, water is still translucent. This is the easiest fix.
- Dark green — heavy algae bloom, you can’t see the bottom. Fixable, takes 4–7 days.
- Black or brown — advanced algae plus organic debris. Sometimes fixable, sometimes better to drain.
If your pool is so dark you can’t see the second step, or if there’s a lot of visible debris on the floor, call a pro. Trying to shock a heavily contaminated pool wastes chemicals and time.
Day 1: Skim, Brush, and Balance the Water
Skim the surface. Manually vacuum any visible debris to waste (not through the filter). Test the water — you’ll almost certainly find low chlorine and high pH. Balance pH to 7.2 (slightly low, so the shock works harder) and alkalinity to 80 ppm.
Day 2: Shock — Aggressively
This is the step where DIYers go wrong. You need a lot of shock. Rule of thumb: triple the dose recommended on the label for the pool volume. Use unstabilized calcium hypochlorite or liquid chlorine (not stabilized shock — you already have plenty of cyanuric acid in a stagnant pool).
Add at dusk, with the pump running, and keep it running 24 hours. Brush the walls twice — once before, once after adding shock.
Day 3–4: Filter Cycle
Run the pump continuously. Backwash or clean the filter every 8 hours as it starts collecting dead algae — the filter pressure will climb fast. Keep chlorine at 5 ppm minimum.
You should see the water shift from green to gray/cloudy by day 3. Cloudy is a good sign — it means the algae are dead and getting filtered out.
Day 5–7: Polish and Stabilize
Once the water is mostly clear, add a clarifier or flocculant to gather remaining fine particles. Continue running the filter and brushing daily. Retest and rebalance chemistry to normal targets (pH 7.4–7.6, chlorine 1–3 ppm).
If cloudiness persists after a week of aggressive treatment, the filter media may be exhausted (especially DE and cartridge) — replace it.
When to Call a Pro
Green recovery seems simple on paper, but three things go wrong for DIYers:
- Under-dosing shock (afraid of wasting chemicals)
- Not brushing enough (algae hide in surface texture)
- Not cleaning the filter often enough during recovery (dead algae clog it fast)
If you’re two days in and not seeing progress, or if the pool is so bad you can’t see the bottom, save yourself the chemistry costs and call us. We recover green pools every week and can usually have yours swimmable in 48 hours. Free assessment here.