You walk outside, look at your pool, and it's green. Maybe it happened overnight after a storm, or maybe it crept up over a few days. Either way — don't panic. A green pool is fixable. But how you handle it matters a lot.

This is our most common emergency call in Collin County. Here's exactly what to do — and what to avoid.

Why Is My Pool Green?

Green water is almost always algae. Algae blooms when chlorine levels drop too low — usually due to:

Heavy rain diluting your chemicals
Extended hot weather burning through chlorine faster than normal
Pump or filter not running long enough
Skipped maintenance during a busy week
Algaecide resistance from repeated use of the same product

This is exactly why consistent weekly pool maintenance is so important — it prevents the conditions that allow algae to take hold in the first place.

Step-by-Step: How to Clear a Green Pool

Test Your Water First

Before adding anything, test your pH, alkalinity, and chlorine levels. You need to know what you're working with. Shocking a pool with a high pH is a waste of money — chlorine is far less effective above pH 7.8.

Balance pH and Alkalinity

Get pH between 7.2–7.4 and alkalinity between 80–120 ppm. This makes your shock treatment dramatically more effective.

Shock the Pool — Heavily

Use calcium hypochlorite shock (not liquid chlorine) at 2–3x the normal dose for a green pool. For a severely green pool, you may need 3–4 lbs per 10,000 gallons. Shock at dusk so sunlight doesn't burn it off.

Run Your Pump 24/7

Keep your pump running continuously until the water clears. This circulates the shock and pushes dead algae through the filter.

Brush Everything

Brush walls, floor, and steps to break up algae colonies. Dead algae sitting on surfaces won't clear on its own.

Clean or Backwash Your Filter

Your filter will get loaded with dead algae. Clean or backwash it every 12–24 hours during the clearing process. Learn more about filter maintenance in our filter cleaning guide.

Add a Clarifier

Once the water turns from green to cloudy blue/white, add a pool clarifier to help the filter capture the fine particles.

Common Mistakes That Make It Worse

Draining the pool

Draining can cause your pool shell to crack or pop out of the ground. It's almost never necessary and always risky.

Adding algaecide before shocking

Algaecide is a preventative, not a cure. Adding it to a green pool before shocking is ineffective and wastes money.

Using liquid chlorine as your only shock

Liquid chlorine is 10–12% concentration. Cal-hypo shock is 65–73%. For a green pool, you need the stronger stuff.

Shocking during the day

UV rays from the sun break down chlorine rapidly. Always shock at dusk or after dark for maximum effectiveness.

Stopping treatment too early

The pool may look clear but still have algae spores. Keep chlorine elevated for 48–72 hours after it clears.

How Long Does It Take?

A light green pool can clear in 24–48 hours with proper treatment. A dark green or black pool (severe algae bloom) can take 3–7 days of continuous treatment and filter cleaning.

If your pool isn't clearing after 48 hours of treatment, something else is likely going on — a broken filter, a chemistry imbalance, or a more resistant algae strain. That's when it's time to call a pro.

Green Pool Emergency?

Green pool cleanups are our most common emergency call. We respond in less than 24 hours, diagnose the root cause, and get your pool back to crystal clear as fast as possible.

Call Now — 469-947-7501