Having a green pool is every pool owner’s nightmare. The water becomes murky, unpleasant to swim in, and can even become a health hazard if left untreated. So how long does it take for a green pool to clear up and become swimmable again? There are several factors that determine the answer.
What Causes Green Pool Water?
Green pool water is caused by an overgrowth of algae. There are a few different types of algae that can bloom in a swimming pool, turning the water a greenish color:
- Green algae – This is the most common type that forms in pools. It multiplies rapidly in the presence of sunlight and nutrients.
- Mustard algae – Also known as yellow algae, this type produces yellowish-brown water.
- Black algae – Least common but very difficult to get rid of.
The main factors that contribute to algae growth include:
- Sunlight – Algae needs sunlight to photosynthesize and grow.
- Heat – Warm pool water temperatures promote faster algae growth.
- Stagnant water – When the pool water is not circulated and filtered properly, algae can thrive.
- Improper chemical levels – If chlorine and pH levels are off, it creates the perfect environment for algae.
- Nutrients – Phosphates and nitrogen from swimmer waste, leaves, and other debris act as food for algae.
When several of these factors are present, the algae can quickly get out of control, turning the pool into a swampy green mess.
How Long It Takes a Green Pool to Clear Up
The time it takes for a green pool to become clear again depends on a few variables:
Type of Algae
- Green algae – Typically takes 1-2 weeks to clear with proper treatment.
- Mustard algae – Can take 2-3 weeks to fully get rid of.
- Black algae – Very stubborn, usually takes 3-4 weeks to clear.
Black algae is the most challenging type to remove from a pool. If black algae is present, it will likely take the pool longer to return to a sparkling blue color.
Extent of the Algae Bloom
If the algae is caught early before it becomes widespread, the pool will clean up faster. However, if the algae has been left unchecked for a while and is thickly coating all surfaces, cleanup will be slower.
For pools with severe algae blooms covering the entire pool, walls, and floor, it can sometimes take over a month to get back to normal clarity.
Filter Type and Run Times
Having an efficient filtration system that runs long enough every day helps clear green water faster. Here is how different filter types compare:
Filter Type | Effectiveness |
---|---|
Sand filters | Less effective, longer clearance time |
Cartridge filters | Moderately effective |
DE filters | Very effective, faster clearance |
Diatomaceous earth (DE) filters are the best at trapping algae and preventing it from recirculating in the pool. Running any filter less than 6 hours per day will slow the clearing significantly.
Pool Volume and Circulation
For very large pools or very small filter systems relative to the pool volume, it will take longer for the green water to be fully filtered out. Pools with better circulation that turns over the entire water volume at least once per day will see faster results.
Weather Conditions
Because algae thrives on sunlight and warm temperatures, cooler or cloudier weather will inhibit growth and allow chlorine to work more effectively. Hot sunny weather can cause algae to bloom again and may prolong the clean up process.
Chemical Treatment
Proper chemical treatment is crucial for clearing green pool water. Here are tips for chemistry:
- Maintain chlorine level at the top of ideal range (3-5 ppm) until algae is gone.
- Keep pH in balance (7.4-7.6).
- Shock treat with granulated chlorine or potassium monopersulfate.
- Brush walls and vacuum pool frequently to remove dead algae.
- Confirm phosphates and nitrates are not present.
- Use algaecide products for stubborn cases.
Following these guidelines for chemicals, along with running the filter continuously, will ensure the fastest clearing time.
Step-by-Step Process to Clear Up Green Pool Water
Here is a step-by-step guide to clear up green pool water:
- Test water chemistry – Check current chlorine, pH, cyanuric acid, phosphates, and nitrates. Make adjustments to get all levels ideal.
- Shock treat the pool – Use 3-5x the normal dose of shock, depending on algae severity. Granulated chlorine or potassium monopersulfate work best.
- Brush walls and floor – Scrubbing will loosen algae so it can be filtered out. Pay extra attention to problem spots with thicker algae.
- Run filter 24/7 – Run your pool filter continuously until water clears. Backwash as needed to prevent clogging.
- Add algaecide (if needed) – For difficult cases, use a concentrated algaecide. Be sure one is safe for your pool type.
- Use clarifier (if needed) – A clarifier bonds tiny particles together so they can be trapped by the filter.
- Vacuum to waste – Vacuuming debris to waste removes algae so it can’t return to pool.
- Maintain chemical levels – Check chlorine, pH and other chemicals daily. Keep chlorine at the top of ideal range.
- Repeat process – It often takes several rounds of shocking, brushing, filtering, and vacuuming to completely clear all algae.
This rigorous process will clear even severe green pool water in 1-4 weeks typically. Stay diligent until the pool water is crystal clear again.
Preventing Green Water in the Future
Once you finally get your pool sparkling blue again, you’ll want to prevent the dreaded green monster from returning. Here are some tips:
- Maintain proper chlorine level (1-3 ppm) and pH (7.2-7.8) weekly.
- Shock treat weekly or as-needed to maintain chlorine level.
- Check cyanuric acid level monthly, keep between 30-50 ppm.
- Brush walls and vacuum regularly to prevent algae growth.
- Clean pool filter at least monthly according to manufacturer.
- Use algaecide preventively during hot sunny weather.
- Address low pump flow issues causing poor circulation.
- Cut back trees and foliage to reduce shade and falling leaves.
Staying on top of chemicals, cleaning, circulation, and maintenance will help keep your pool water clear, sparkling, and free of algae.
When to Call in a Pool Professional
In severe cases of green algae blooms, it can be helpful to have a pool pro assess the situation. A pool service can check:
- Circulation efficiency and filter function.
- Chemical levels and balance.
- Source of any underlying issues like leaks.
- Determine if special treatments or equipment may be needed.
For pools that stay green despite your best efforts, calling a pool company can save lots of frustration and ensure the right procedures are followed.
Some instances when you may want to consider professional help include:
- Pool is still green after 2-3 weeks of treatment.
- Water won’t clear even with excessive chemical use.
- Algae returns shortly after cleaning up.
- Pool has black algae.
- Water feels slimy, indicating a severe algae problem.
- Filter can’t keep up with the algae load.
- Green water is triggering asthma or allergy symptoms.
A reputable pool service can assess the green water, advise on the best clearing methods, and even provide the necessary algaecides and boosters to get your pool healthy again. This is especially helpful for first-time pool owners contending with a major algae issue.
FAQs on Clearing Green Pool Water
Does chlorine alone clear green pools?
Chlorine is essential but not solely effective against green pool algae. The combination of chlorine shock, algaecides, clarifiers, scrubbing, filtering, and vacuuming to waste works best to clear all algae and prevent recurrence.
Should I drain a green pool and start over?
Draining and refilling a green pool is usually not necessary. In most cases, the pool can be cleared up faster by treatment and cleaning rather than draining. However, if black algae is present and persistent, draining may be the best option.
Can I swim in a pool while it’s green?
It’s best to avoid swimming in a green pool until it is completely cleared up. The algae can cause skin irritation, rashes, and eye redness. Also, levels of chemicals used for treatment may be at unsafe levels for swimming until the pool is ready.
How often should I shock a green pool?
During initial green pool treatment, shocking needs to be very frequent – sometimes even daily. Shocking 2-3 times per week is often needed in severe algae cases. Once the water begins clearing, ease back to weekly or as-needed shocking.
What if it’s still green after shocking repeatedly?
If heavy shocking isn’t making a dent, the issue is likely poor circulation. Ensure the pump and filter are running 24/7. Clean or backwash the filter regularly. Check for low flow issues preventing good water turnover. Increase algaecide dosing as well.
Conclusion
A green swimming pool is a major headache. Depending on the specific algae type and extent of the bloom, along with your pool size and equipment, it can take anywhere from 1 week to 1 month to regain crystal clear water. Maintaining proper chlorine, pH, and circulation are key to clearing green water in the fastest timeframe. Vigilance is required even after the pool looks clean to prevent algae from recurring. Calling on pool professionals for assistance can be wise to address difficult green water cases. With some persistence and elbow grease, you can defeat the green monster plaguing your pool.