Why Is My Pool Green and Cloudy Even After Shocking?

Updated on May 20, 2019
robhampton profile image

Rob is a pool-service industry professional with over 20 years of experience.

A Cloudy, Green Pool
A Cloudy, Green Pool

Judging from the questions pool owners ask on the internet, they are having a hard time with water clarity even when they think all the chemicals are balanced. We will discuss in this article why chlorine, pH, and alkalinity are only the beginning in maintaining clear pool water, and then we will troubleshoot the problem.

In this article, you will find answers to the following questions:

  1. I Shocked My Pool, So Why Is It Still Cloudy?
  2. I Shocked My Pool, So Why Is It Still Green?
  3. How Much Shock Should I Add to the Pool? Did I Add Enough?
  4. Will the Pool Turn Green If I Don't Add Chlorine?
  5. How Long Should I Run the Pool Pump? Am I Filtering My Pool Enough?

Basic Chemical Requirements for Clear Pool Water

Just to summarize, these are the basic chemical requirements for a pool that stays clear. But there is a little more to it than the basics, as you can see in question 2 below.

  • Free chlorine. Unless the water has a sufficient level of free chlorine, algae will grow and make your pool green and cloudy.
  • Correct pH. For normal use, your pool’s pH should be between 7.4 and 7.6: for shocking, it should be between 7.2 and 7.6. Shocking a pool with too high pH will cause cloudiness.
  • Correct alkalinity. The right range of alkalinity (dissolved salts that keep pH stable) makes pH and chlorine levels easier to maintain.

So What Do I Do Now With My Green and Cloudy Pool?

Read each of the five questions below: at least one should relate to the problem you are having. Most of these questions are based on real keyword searches that have found some of my articles.

Just to summarize my experience: a bad filter is the most common cause of cloudy pool water. Green pool water is caused by a bad chemical balance, usually something other than just low chlorine.

1. I Shocked My Pool, So Why Is It Still Cloudy?

If your pH is not too high, filtration issues are likely the cause of your cloudy pool. The issue may depend on the type of filter.

  • If you have a sand filter, it could take a week or more for the pool to completely clear. That's even if it's a working sand filter.
  • If you have a cartridge filter, it needs to have a good cartridge. A cartridge can only handle so much. If your pool is cloudy, the cartridge needs to be cleaned DAILY until the pool is clear.
  • If you have a diatomaceous-earth (DE) filter and the pool is cloudy, then
  • either the pump is not being run on a long enough cycle,
  • the DE is not fresh because it’s not being backwashed,
  • or the filter is defective and not working properly. (Do you have torn filter grids? A broken manifold? Does DE powder shoot back into the pool when you add it? If so, the filter needs to be taken apart and cleaned or repaired, and your pool will remain cloudy until the repair is made.)

So remember, a cloudy pool can be caused by a bad filter.

If the pool is being filtered properly, you won't need a clarifier solution. In some cases, you can use a flocking agent, a product called "drop out" or "drop and vac," that will bind small particles together and sink all of the algae to the bottom of the pool where it can be vacuumed up as waste.

Green, Cloudy Pool
Green, Cloudy Pool | Source

2. I Shocked My Pool, So Why Is It Still Green?

This is one of the most often searched questions. High levels of the wrong chemicals may be the issue. Let's take a look at reasons why your pool may still be green even after you've exhausted yourself adding tons of chemicals.


Over time, if you use tablets (like Tri-Chlor) to supply chlorine, levels of the stabilizer from the tablets (cyanuric acid) can become elevated over time and “lock up” the free chlorine molecules (Cl2). Even if you get a very high chlorine reading on your test kit, the chlorine is simply not able to work at killing algae because it’s not in the right chemical form. This article shows you how to lower stabilizer levels.


High phosphate levels can definitely cause algae problems. Phosphorus, or phosphate, can enter the pool by leaching out of leaves or organic debris in the pool, or drifting there from fertilizer sprayed near or around your pool. Because algae feed on phosphates, algae blooms due to phosphorus can become overwhelming in the summer months when the water temperature exceeds 78–82° F. This condition is easily treatable with a phosphate-removing product like this one.

3. How Much Shock Should I Add to the Pool? Did I Add Enough?

"Shocking" a pool that has turned green is better known in the industry as "super-chlorination."

When shocking the pool, consider a few factors. How big is the pool? How "green" is it? If your pool is a normal residential-sized pool of 13,000-25,000 gallons (the pool pictured at the top of the article is around 18,000 gallons), then your options are liquid chlorine or granular shock. The choice depends on what type of filter it has.

  • If it is a sand or cartridge filter I will use liquid chlorine, about 10 gallons, or four of the yellow "Jerry-jugs." The reason I use liquid chlorine is that granular chlorine will leave a residue that is harder to filter out.
  • If the pool has a DE filter, then I will use granular chlorine (about 5 pounds). This article shows how I shock a pool with a DE filter. Remember to test the water before adding shock. The pH should ideally be low when shocking the pool (around 7.2) because shocking the pool will raise the pH level.

Remember that shocking alone does not clear up a green or cloudy pool; that is what the filter is for. It doesn't matter how much shock you put in the pool if you have a bad filter.

4. Will the Pool Turn Green If I Don't Add Chlorine?

Believe it or not, I have seen this keyword search pop up more than once. There is a short answer: YES, IT WILL turn green if you don't add chlorine. Pool water must have a sanitizer or something that will kill bacteria and algae. Algaecide alone without chlorine will not prevent the pool from turning green.

5. How Long Should I Run the Pool Pump? Am I Filtering My Pool Enough?

Always run the pump when shocking the pool and allow it to circulate for 24 hours. The water should then be a blue or cloudy blue color.

Test the water 24 hours after shocking and start adjusting pH and alkalinity levels. The chlorine will still be elevated, but over a few days it should stabilize. To lower the chlorine level, you could add sodium thiosulfate, but I do not recommend this, because adding too much can cause the chlorine level to seesaw back and forth.

After the shocking process is complete, and you are back to normal operation, you need to set your timer so the pool is filtered for a long enough time each day to deal with any algae or debris. How long to run the pump depends on the turnover rate: the time it takes for the circulation system to move the entire volume of water in the pool (the number of gallons) through the filter equipment.

During the hot summer months, an average-size residential pool that is in use should be filtered for a minimum of eight hours. During the cold season (since algae grow slowly in cold water), or when no one is using the pool, the filter time can be cut in half. But the pool water does need to be filtered whether it is being used or not.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

  • I put the hth Super Shock green to blue 1 in my above-ground pool, and now it's light green. What should do I do next?

    After shocking the pool, it will need filtration and circulation. Run the pump as much as possible. Keep the filter clean (daily) until the water runs clear. Be sure to brush the pool often during this process as above-ground pools do not have drains at the bottom. A clarifier solution can also be used to help out.

  • How long do I backwash the sand filter of my pool?

    Sand filters require a longer backwash time than a DE filter. Both work by reversing the flow and blowing buildup and debris to waste (or backwash hose) In my personal experience with sand filters, a solid 2 minutes is sufficient. I have heard that backwashing a sand filter for 5 minutes is good. Unfortunately, you'll lose several inches of water if it's backwashed that long. So, a good tip would be (and this is what I do for sand filters). Backwash for 90 seconds. Bring valve back to filter position and run for one minute. Backwash again for another 60 seconds. Should be good to go after that. If you have a "multi-port" valve then there should be a rinse cycle. Run the rinse for 30 seconds after following the above steps.

  • My pool is green. The alkalinity is 180 and the pH is 6.8. What can I do to make it clear?

    Balancing the chemistry will be the first step. Start with chlorine, pH, and alkalinity. Without knowing the volume (gallon size) of the pool, I can not answer this accurately. Please try this pool chemical calculator for adjustment and dosage amounts.


    After chemicals are balanced, filtration will be the most important factor in clearing the water. Run the pump as often as possible, cleaning the filter every 2 days until pool is clear

  • After vacuuming the pool how long should I wait before checking chemical balance?

    Vacuuming the pool will not affect the chemistry readings. It can be tested before, after or even during vacuuming and the results will be the same.

  • I have an above ground 24 x 52 round pool. I have cleaned the pool and started with clean water. We have rust in our water. I have put 32 ounces of algaecide along with 4 shocks, and 5 bottles of chlorine. The water is green. I have a sand filter with brand new sand. What can I do?

    Above ground pools can be difficult when trying to get rid of algae, only because there is no "Main drain" or a drain at the bottom of the pool which helps the filtration process greatly. An above ground pool usually only has a surface skimmer. If you've started with clean water, small amounts of chlorine should be added while filling. As far as rust being in the water, you need a metal sequestering agent which will remove the metal from the water. There are a couple of different ways to address the "green" in the pool. Since you have a sand filter, there should be a backwash mode in which the water is pumped to waste. Ideally, if your filter is equipped with a "multi-port" valve, then there should also be a "waste" setting on the valve. Brush the pool, add a floccing agent (this will drop all algae to the bottom of the pool) and then vacuum everything that has dropped to the bottom out to waste. Another option would be to brush the pool often and run the filter as much as possible. Unfortunately, sand filters have a higher micron count and take much longer to clear a green pool, especially if there is no main drain. The water would need to be continuously stirred up to be able to filter it through the surface skimmer. If all else fails, drain the pool and re-fill being sure that a metal sequestering agent is added to counteract the rust in the water.

© 2012 Rob Hampton


Submit a Comment
  • robhampton profile imageAUTHOR

    Rob Hampton 

    8 months ago from Port Richey, Florida

    Hi Amy. Bad filtration is normally a common cause for pools not clearing up. If you have a cartridge filter, you may want to replace the cartridge. Clean the cartridge every few days until the water clears. If you have a DE filter, might want to think about taking it apart and servicing it. This is about all the advice I can give at the moment without knowing more about what type of filter system being used

  • profile image

    Amy Hunk 

    8 months ago

    Our pool is 40,000 gallons. I have tried all summer to get it right. Finally, all levels are perfect (ph, alkalinity...), but the water is still a real color! I take water samples to a local supply store to be tested. The chlorine level was a little high, but I had recently added shock. I’m about ready to fill this thing in with dirt! HELP! What will turn this water blue if everything is supposedly right???

  • robhampton profile imageAUTHOR

    Rob Hampton 

    9 months ago from Port Richey, Florida

    Hi Barry. Anytime you can vacuum debris, dust or algae to waste, it's always a good thing! Thanks for reading... Rob

  • profile image


    9 months ago

    I gravity vac my pool where I fill the vac hose then the end goes outside the pool to drain the waste from the pool. is this good

  • profile image

    Leah Martin 

    9 months ago

    How do I know if my filter is bad? We have an ingound salt water pool that is about 20,000 gallons. We had some nasty storms and now our pool is black on one end and flourescent green on the shallow end. We have shocked, flocced, added anti algae treatments. Cleaned the filter and the chlorinator. Nothing is working. I am about $600.00 in the last 2 weeks on chemicals. What can we do now?? Please help!

  • profile image


    9 months ago

    "Sometimes people don't like to hear this, but in this case the only advice I'm going to give is to drain pool and start over. By the time you exhaust all of your time, energy, and cost of chemicals it will be worth the cost of some water."---Yeah, I'm one of those 'sometimes people'. My wife wanted the above ground pool, and she has trouble keeping the water clear (sand filter). Last year, she filled it up 3 times, and each time filling it up is an extra $100 on the water bill. I'm really starting to hate that pool. In 2019, you'd think there would be a better answer than 'better to empty it and fill it up again'

  • robhampton profile imageAUTHOR

    Rob Hampton 

    9 months ago from Port Richey, Florida

    Nana Dora, thanks for reading. The best course of action would be to use Soda Ash (sodium carbonate). This, unlike sodium BI-carbonate (baking soda) will raise the pH without raising alkalinity. Use small amounts until pH is around 7.4. maintain this pH and the alkalinity will eventually decrease on its own. Hope this helped.

  • profile image

    Nana Dora 

    9 months ago

    Help PLEASE, my pool is 10500 gal, I’m having a hard time bringing PH up, and lowering my alkalinity ..... any suggestions?

  • profile image


    9 months ago

    I ran into this problem several years ago. My pool was green even at ridiculously high chlorine values. The problem then was that I was using Dichlor labeled as "pool shock" which is basically stabilizer with chlorine attached. I had so much stabilizer that it was keeping the chlorine from doing anything. The only way I got rid of the problem was to drain the pool (for the first time in about 10 years). Now I only use sodium hypochlorite for shock and I haven't had the problem again. I still use trichlor for daily management which has slowly built up my stabilizer since it doesn't every really go away (even in winter).

    I think the biggest reason for this being the highest googled question is the labeling of dichlor as shock. As a one-time beginning of year treatment, maybe. I would be willing to bet that most of the people suffering from the green shocked pool were doing it with dichlor. That's what all the non-pool stores (Costco, Sams, Walmart) have now and it's all labeled "shock".

  • robhampton profile imageAUTHOR

    Rob Hampton 

    10 months ago from Port Richey, Florida

    Hi Diane. It's difficult to answer this question without knowing some things about the pool as treatment methods vary based on certain things such as..is this an in-ground, or above ground? Type of filter? (Cartridge/DE/Sand), Size of pool? (Can it be drained and refilled easily?) You could try floccing the pool. I just can't give a simple answer without knowing these things.

  • profile image


    10 months ago

    We didnt cover the pool this past winter. It turned cloudy blue like milk. Been trying to clear it for two months now. The chemicals are all within normal limits. What can we do?

  • robhampton profile imageAUTHOR

    Rob Hampton 

    10 months ago from Port Richey, Florida

    Ed, thanks for reading. You can view my article on how to floc a pool here. https://dengarden.com/swimming-pools/Cleangreenpoo...

  • profile image


    10 months ago

    You need flock directions will tell you how to use

  • profile image


    17 months ago

    If chlorine is high will the water trun green coz of high chlorine

  • profile image


    19 months ago

    Hi, for the first time in 20 years of owning this pool, we've struggled with cloudy water and algae all summer. We've never before had an issue managing the chemistry, and usually have crystal clear water. Have had the water tested multiple times and local pool store is out of ideas.

    We brush the walls/bottom then shock, then after the water starts to clear, use a floc to settle out the remainder and vacuum to waste. But pool never completely clears, and algae starts to grow again within a week, even with high remaining chlorine (5+ ppm).

    Currently (48 hours after most recent brush and shock) we have:

    Stabilizer: 20 ppm

    Free chlorine: 11.4 ppm

    pH: 7.4

    TA: 120 ppm

    Calcium hardness: 190 ppm

    Phosphates: 0 ppb

    16,000 gallons. Sand filter running 24/7. Sand was replaced in June.

    Pool is green--is the same color it was 48 hours ago when we shocked it, using liquid shock. There has been zero change.

    Help? Any ideas? We're at a total loss, and so is our local pool store!

  • profile image


    20 months ago


    I have a 5500 gallon pool that has had issues staying clear. we have had people fired over and still cant find the issue. we took the water to be tested and shocked it, got all new spider valves. Vacuum it and scrub it every other day. It has rained a a lot however the color started before hand. The temp is around 78, ALK varies from 60 to 80, and the PH Level is 7.4 to 7.6. chlorine has varied a lot in the last week.

    Thaks you

  • robhampton profile imageAUTHOR

    Rob Hampton 

    20 months ago from Port Richey, Florida

    Hi Elizabeth. It sounds like you are having the EXACT same problem as "Kim". Please read the comment I left for her. Thanks

  • profile image


    20 months ago

    I just opened my above ground pool (15ft round x4 ft high) and it was super green and yucky. I purchased a new pump and filter and shocked my pool Sunday night and took some water to the pool store and was told it was locked up so to shock again so I did that last night. I have had the filter running since Sunday afternoon. the pool is still green and cloudy and all levels are showing very low. I don't know what to do next? wait it out? we clean the filter 3 times a day.

  • robhampton profile imageAUTHOR

    Rob Hampton 

    20 months ago from Port Richey, Florida

    Hi Kim. Sorry to hear the pool looks so bad. Sometimes people don't like to hear this, but in this case the only advice I'm going to give is to drain pool and start over. By the time you exhaust all of your time, energy, and cost of chemicals it will be worth the cost of some water. The filter element can only handle so much. It will need replaced soon because trying to filter it all out and cleaning it constantly is very hard on it. There is really no way of me knowing why it's not holding chlorine without being able to do a full range chemical analysis. I hope this helps.

  • profile image


    20 months ago

    HELP! I am very frustrated. We have a pop up 15 x 48 pool. Just got back from a 1 week vaca and the pool was a very dark green from algae growth. I shocked it and added algae killer. Now its been 2 days and it still has some green but VERY cloudy! I am cleaning the filter cartridge 3 times a day. No cover on the pool, exposed to the sun. What am I doing wrong? How long will this take to totally clear up? Why do my test strips say there is NO chlorine in the pool (even though I've shocked and have added 6 oz of chlorine 24 hours later) and the PH is way too high even though I have added PH minus? Do the test strips even work?? Do I now have too much chlorine in it so the strips won't read it??

  • profile image


    20 months ago

    We've tried everything that we've googled, that's applicable. Why is the pool water still green? This has been an ongoing issue for about 3 weeks now.

  • robhampton profile imageAUTHOR

    Rob Hampton 

    20 months ago from Port Richey, Florida

    Hi Tony. Yes. It's dangerous. So many diseases in pool water that is not treated and filtered.

  • profile image

    Tony ure 

    20 months ago

    hi is this colour water dangerous to swim in or just unpleasant because of its look? thanks

  • furniturez profile image


    7 years ago from Washington

    No wonder my neighbors pool is green! Lots of insight thanks so much.


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