How To Clear Green Pool Water In 5 Days Or Less

What's the most common problem facing pool owners?  A bad pump motor?  Maybe a leaking filter?  While those are problems that need to be dealt with, the biggest problem is a green pool.  And it may have happened to you a time or two.  It can ruin your pool, your weekend, and quickly drain your wallet.  Have you been there yet?  If the proper steps are not taken to avoid, eliminate, and control your pool algae, it can reproduce like rabbits and drive up your pool maintenance cost.

How To Clear Green Pool Water In 5 Days Or Less

Why Do I Have Green Pool Water?

Green pool problems are normally a direct result of poor swimming pool water chemistry, pool water maintenance and/or bad filtration.  Your pool can go from crystal clear to green seemingly overnight.  And what's the main reason?  Pool algae.  And what's the main cause?  Pool algae can happen when the pool’s sanitizer levels are too low for too long, or the sanitizer is simply not effective at killing off the algae spores. 

By not keeping up with pool water testing and water balancing, if you're not adding enough chlorine, or the chlorine you're adding is not effective, there's a huge chance you're going to end up with green pool water.

Is Green Pool Water Harmful To Swim In?

Algae, in and of itself, might not be harmful.  People have actually eaten algae for hundreds of years.  But where there's algae, there's bacteria, and that most definitely can make you sick.  Green pools might also harbor bacteria, viruses, parasites and other pathogens, which could possibly make you sick.  They can enter a swimmer's body by way of the eyes, ears, nose, throat, and even a small skim cut.  The result of swimming in green pool water could intestinal problems, stomach aches, infections, fever, and diarrhea. 

How To Fix A Green Pool

A green pool is different than mustard algae and should be treated accordingly.  Green pools are more common, but it's not common when it happens to you, so here we go.

1. Clean The Filter

We'll never clean dirty water with a dirty or non-working filter or filtration system, so let's get the filter clean.  Backwash your sand or DE filter.  If you have a cartridge filter, make sure you take it out and clean it well.  Never use a power washer on a cartridge filter.  That's too much pressure and you're not gaining anything by using it.  If your sand is old, you might need to replace it.  If your cartridge filter is old, or has more than 3,000 filter hours on it, you'll need to replace that as well.  Make sure you recharge your DE filter with fresh DE after backwashing.  

2. Remove Everything From The Pool

Remove and wash bathing suits, toys, floats, and anything else from the pool.  Wash your bathing suits in a washing machine and dry them in your dryer.  Wipe down everything you removed with a 50/50 solution of bleach and water.  You can use a scrub brush  for a more thorough cleaning.  Place your pool cleaning equipment (telescopic pole, net, brush) in the pool so that it becomes sanitized.

3. Test and Balance Your Pool Water

Adjust your pH, alkalinity, and calcium hardness.  Your pH should be 7.0-7.2.  Chlorine is more active at a slightly lower pH level.  Adjust your alkalinity to 80-120 ppm and hardness to 150-250 ppm.  Remember to maintain your CYA level at 30 - 50 ppm.  I use and recommend the Taylor K-2006 test kit.  

4. Brush The Pool With A Nylon Brush

Green algae will try its best to stick to your pool surface, so give it a good brushing at least twice per day.  If you have a plaster or concrete pool, go ahead and use a wire brush.  Never use a wire brush on a vinyl or fiberglass pool. 

5. Shock Your Pool

Increase and maintain a free chlorine level of at least 20 ppm using liquid pool chlorine or bleach.  Your chlorine level will always decrease, so it's important to keep an eye on the chlorine level and keep it high.   

6. Always Filter 

Keep that pump motor on 24/7 until the entire process is finished.  All of those dead and dying green algae particles are going to be floating in your pool water and they need a place to go.  That place it in your filter where they'll be trapped and waiting to be cleaned or backwashed out.  

 7. Clean The Filter

Now your filter has captured much of the dead and dying green algae and that yucky stuff needs to go somewhere.  That somewhere is out of your filter.  So backwash your sand or DE filter or clean your cartridge filter again.

8. Shock Your Pool Again and Brush Very Well

Let's remember that shocking a pool is a process, not an event.  Your chlorine level will always be decreasing so maintaining a high chlorine level is a must in order to kill the green algae.  

9. Test and Balance Your Pool Water

After all that work your green pool water should be in the past.  Now it's time to balance your pool water once more.  Your chlorine might be a little on the high side, but it'll decrease in time.  Next, your pH might be above the normal range of 7.2 - 7.8.  A little muriatic or dry acid will bring it back in line.   

Easy pool maintenance

How To Prevent Green Pool Water From Returning

"An ounce of prevention is worth a pound of cure."  This is so true with green pool water.  Your first line of defense is to always wash your swim suits in hot water and clean all pool toys with a 1/2 and 1/2 mixture of bleach and water.  And never put anything in your pool that's recently been in the ocean, river, or stream.  For more preventative measures you can: 

  • Maintain your alkalinity, pH, and sanitizer levels in the recommended ranges 
  • Run your pump and filter for 8 to 12 hours a day all season long 
  • Regularly vacuum and brush your pool 
  • Keep all pool accessories clean including pool toys, floats, and anything else that goes in your water 
  • Practice proper hygiene by taking a soapy shower before swimming.  Ask your swimming guests to do the same. 

Final Thoughts On Green Pool Water

That was a lot of work.  I know how exhausting fighting green pool water can be.  I've done it over 700 times for my customers.  More importantly, you'll have a safe and clean pool to swim in.     

Common Questions About Clearing Up A Green Pool

In this section you'll find answers to some common questions I've received over the years.  

Swimming Pool Phosphate Level Over 1000

QUESTION: We bring our pool water in to be tested every week.  Suddenly the last 3 weeks the phosphates are thru the roof (Pool guys words) and has us adding a product to lower it.  Have done this three times...they checked the house water.. says it's good..  WHAT EXACTLY RAISES THE SWIMMING POOL PHOSPHATE LEVEL? WHAT ARE THEY?  Can chlorine affect the level??? We are soooo confused and yet, the pool is crystal clear!!!

ANSWER: Algae needs phosphates and nitrates to reproduce, grow, and spread. So basically phosphates are food for algae.  You get swimming pool algae and green pool water when the swimming pool chlorine level is low. You always want to keep your pool chlorine level between 2 - 4 ppm and your cyanuric acid level (CYA) between 30 - 50 ppm.  Your pool guy is telling you to add some kind of phosphate remover. One of the more popular kinds is named Phosfree. A 32oz. bottle will normally run about $32, basically $1 per oz.

You can get a test kit for phosphates. This kit normally runs about $12 and is very easy to use. You simply fill a vial with pool water, put a pill or dry mixture in the vial and shake it for about 1 minute. The water will turn a shade of blue, then you match the blue pool water with  the comparison chart provided in the kit.  White or very light blue indicates a low phosphate level and a dark blue indicates a high level of phosphates.

I'm not a big fan of phosphate removers. I think they should only be used in extreme circumstances and here's why.  Your pool chlorine is the sanitizer for your pool, meaning it kills the bacteria and organic matter in the pool, including pool algae. This matter is then trapped in the swimming pool filter and is backwashed away. This is a fact that all pool guys will agree with.

When your swimming pool chlorine is the right level, between 2 - 4 ppm then there shouldn't be any swimming pool algae, right?  If the pool chlorine is doing its job in killing this organic matter, and there's no pool algae, then why should you worry about the phosphate level? There's no swimming pool algae to eat up the phosphates because the pool chlorine is killing the algae on contact.

The YMCA pool that I still operate has a slightly higher phosphate level but it doesn't concern me because I keep the chlorine level between 3.5 - 4.5ppm. We've never had a pool algae outbreak or green pool water because the pool chlorine level is always kept at optimum range.

How Do I Get Red Algae Off A Swimming Pool Solar Cover?

QUESTION: We were gone for 5 days and left our pool running with the solar cover on. Upon return the pool temp. was 91 and we had developed red or pink algae.  We have worked for 2 weeks getting the algae out of the pool, I have cleaned & bleached the pool floats, brushes and swimsuits. The algae is gone but the air temp remains very hot.  We have not needed the solar blanket and will not for a while. It is rolled up.  How can I clean the solar blanket to avoid reintroducing the red algae in my pool? We do not have a large enough deck to spread it out all at once.

I was wondering if when it does get cooler if it would work to super shock the pool and pull the cover over the pool or would that just cause the red algae to return?

ANSWER: In the years I did pools in Arizona I never have had to remove algae from a solar pool cover, but I've talked to a few guys who did.  One of them spread the cover out and sprayed it first with a garden hose to remove any debris and loose algae.  He filled a spray bottle with 1/2 water and 1/2 Clorox bleach then sprayed/saturated the entire cover, allowed it sit for about 5 minutes, then rinsed the cover off.

The 2nd guy took a big 75 gallons trash can and filled it with water and 1 cup of granule chlorine.  He then rolled up the liner, put it in the can, and waited about 2 - 3 hours. He took the liner out and flipped it over to saturate the other side of the liner.  Allowed another 2 - 3 hours, took the liner out, and sprayed it off.  Both the them said this technique worked for them.

High Phosphate Levels And Low Chlorine Issue

QUESTION: I have an in ground chlorine pool approx. 25,000 gallons.  I have high phosphate levels and some level. I have 0 chlorine in my water, however, my cholorinator has tablets in it and it seems to be functioning correctly.  I have a history with phosphates and know that it is the culprit to my chlorine issue. I do have some issue with algae now. I put in some algae treatment on Saturday AM after we vacuumed and swept pool. Saturday night I put in two 48 oz. bottles of PhosFree as directed.  Today is Monday and I still do not have any chlorine in my water and algae is coming back. HELP me before I drain the darn thing and fill it in with dirt!!!

ANSWER: Basically, phosphates are food for algae. Many people believe that they need to keep the phosphates down by adding Phosfree. This is to remove the phosphates. But, if your chlorine level is kept between 2 - 4 ppm, then there will be no algae, so it really doesn't matter what level the phosphates are.  The post above explains that in a little more detail. First, you need to shock with Dichlor. This is a fast acting chlorine with a stabilizer (cyranuric acid/CYA) in it. You'll want to get your CYA between 30 - 50ppm.  Use a Taylor FAS-DPD K-2006 test kit. It's the best and the one most pool professionals use.

The chlorine tab page has the Dichlor information you need and the chlorine page has a chart for shocking your pool.  The question says you used an "algae treatment".  I will assume this is an algaecide. Remember that algaecides are used for preventative maintenance only.  They're not going to get rid of an algae problem or green pool water.  While you're shocking the pool, the algae will be eating up the chlorine so you'll need to manually dose and test your pool each day.  Try to keep the chlorine level up around 8ppm while this is happening.  You can also use a good PolyQuat 60 algaecide as an insurance policy for algae while you're going through the shock process.

This contains no copper or other metals and is safe for vinyl pool liners.  Make adjustments at night, allow for a complete turnover of the pool water.  This is normally around 8 hours, retest, and make another adjustment.  The algae will turn a white/grayish color.  Brush the walls and floor the best you can to loosen up algae that might be sticking. And backwash once per day.  You want to keep the filter cleaned out.  And keep an eye on the pool water level.  You'll be backwashing and losing some water.  The water level should be 1/3 - 1/2 from the bottom of the skimmer.

Once everything is stabilized there shouldn't be any need to add Phosfree because you'll have a constant stream of chlorine in the pool to kill bacteria and algae.  Hope this helps and have a fun and safe swimming season.

How Do I Clear Up My Well Water In My Pool.  My Pool Water Is Green. 

QUESTION: First I started filling the pool and the water had a little yellow color.  Then we went to the pool store which told us to use Metal Magic algaecide and shock.  First we put Metal Magic in.  We ran pump for 48 hrs and then we added the algaecide. Ran pump 12 hrs then we added the shock.  The pool still hasn't changed.... what can we do?

ANSWER: We first need to understand what each product does.  A metal sequestrant does not remove metal from pool water. It holds it in solution until it can get filtered. Then you backwash the metal out.  Because metal sequestrants break down over time and get filtered and backwashed out, you need to weekly dose your pool if you have high iron and copper.  Metal sequestrants that are based on HEDP, phosphonic acid or something similar are the most effective.

Jack's Magic Blue, Purple, and Pink Pink Stuff, Metal Magic, Metal Free, & Metal Klear are very good.  Be sure any algaecides you use don't have any metals or copper in them. You don't want to add to the problem.  An algaecide does not remove green pool water or kill algae. It is used for preventative measures only, normally on a weekly basis.  You can use a PolyQuat 60 algaecide when shocking a pool as added insurance against an algae bloom because the algae will be consumed by the chlorine.

Your chlorine level will drop very quickly, so using an algaecide during the shock time is good.  Shocking a pool, then a daily manual dose of chlorine to keep the chlorine level up while the algae is being killed is the only way to get rid of an algae bloom and green pool water.  Daily brushing and backwashing is also recommended.  It's best to put in the metal sequestrant and allow for a complete turnover of the water. At this time you'll want to backwash.

You did run the filter for 48 hours, which is what you want to do. Keep filtering and backwashing.  A 2nd dose of sequestrant might do you well. Allow for another turnover of the water. This is normally around 8 - 10 hours.  Then do your shock.  Because of the constant backwashing, your water level will drop. Be sure to keep your pool topped off.  1/3 - 1/2 up from the bottom of the skimmer.  Keep an eye on your stabilizer (cyanuric acid/CYA) because if you're putting in fresh water, you'll be diluting any CYA that's already in the pool.

This should be kept between 30 - 50ppm.  It's this time that you'll need patience. There's really no "quick fix" when dealing with pools. It does take time and effort.  Keep filtering and backwashing.  Try to add chemicals in the evening and retest in the morning.  Hope this helps and let me know how it turns out for you.

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