Green Swimming Pool Water – Treat It With These 4 Simple Steps!

by T. Duff on March 31, 2011

Lets face it, every pool will experience green water at one point or another. The main mission when this takes place is two fold. The first is how to treat the water as effectively as possible to get it clear again as quickly as possible. The second item that needs attention is we want to make it happen without breaking the bank. If you go down to your local retailer there’s more shocks, phosphate treatments and water clarifiers than one knows what to do with. Not to mention the countless “novelty” chemicals that are available that can cost an arm and a leg!

When treating green swimming pool water, there are 4 key steps that need to be addressed. Let’s dive in!

Treating green swimming pool water step #1: Circulation. Water circulation is an absolute must. You can add all the shock and other chemicals you want, but if water movement isn’t taking place, it won’t change the look of the water. While you’re turning the pool around, run the equipment 24/7. For most standard residential swimming pools, this will allow for about 3 full water rotations. Meaning, that all of the water will have gone through the filter about 3 times.

Treating green swimming pool water step #2: Shock treatment. Ideally, shoot for a granular shock because it has the fastest reaction time. I’d recommend using HTH Super Shock that contains at least 65% available chlorine. The more available chlorine, the more effective (and faster) it will be in the pool water. It’s important to stress that one cannot over shock a swimming pool. Depending on how green the water is, I’d recommend starting with 3-4 lbs of shock, wait 2-3 hours, then check what the water looks like. There’s no need to test the water at this point using a test kit as the results will be meaningless…regardless how much “free chlorine” it’s showing present.

Treating green swimming pool water step #3: Filtration is key. The more effective the filter is throughout this process, the faster the water’s going to get clear again. The best way to ensure this is taking place is to backwash/clean your filter several times a day. You cannot over-backwash your filter. If you’re using a DE or sand filter, place the multi port valve in the backwash position and let it run for around 90 seconds or until the water is clear. This may take a bit longer depending on the duration of time between backwashes. If you have a cartridge filter, remove the dome of the filter (typically, there’s a band clamp that needs to be removed), lift the cartridge filter(s) out of the filter unit and thoroughly clean it.

Treating green swimming pool water step #4: As the water begins turning clear (still may be cloudy, but blue (not green), begin administering a quality water clarifier. This will speed up the process to getting clear water again. I’d recommend adding it the first time immediately once you notice the water is blue and not green, then again about 12 hours later. During this process continue running the equipment nonstop. During this time you should also be stabilizing the pH and Total Alkalinity levels. I wouldn’t worry about testing or adjusting free chlorine as it’s likely going to be elevated for a few days while the water adjusts, but it is important to test and adjust your pH and TA levels.

I hope you’ve enjoyed these 4 steps on getting your water cleared up as quickly as possible. Using this system, it’s possible to turn your green swimming pool water around in 48 hours or less!

{ 28 comments… read them below or add one }

Brandy Q April 4, 2011 at 2:52 pm

Perfect timing for this article! It’s just getting warm enough to a point where people are reluctantly pulling off the insulating cover and finding green water. =)


Betsy Noel April 5, 2011 at 3:46 am

I have an above ground 24 footer. Although my pool is still covered up, I’ve decided to open it at the end of April, keeping it covered with the solar cover. My dilemma is, I have to use city water to fill lit back to the top (it’s lowered to under the return line). I replaced my liner last Spring and filled it up – and fought algae ALL SUMMER. Found out that the city has quit using chlorine to treat the water, so we had algae problems in the city water. What would be the best way to treat the water once I get it filled? I certainly don’t want to go through that again!


Sharon Warrick April 5, 2011 at 6:17 am

My problems come from a constant 2 months nearly of yellow pollen falling from trees. And of coarse from the yellow it goes to an old black and it stains the pool if I miss any on the vaccuuming. Of course from this comes the mustard algae. I can not work this pool enough this time of year it is constant skimming and vacuuming. In this area the water warms pretty fast and swimming normally starts earlier. We also have our hot tub connected to the pool. Is there a way I can just run and filter my hot tub this time of year and get the pool a little later? Or is this advisable?
Thanks so much,


fireyourpoolguy April 5, 2011 at 7:35 am

Hi Sharon,

It really depends on how the plumbing is situated to run the hot tub & swimming pool. Often, there’s separate equipment for each body – if this is the case, you can run each independently of the other. If not, you’ll need to make sure you’re maximizing water flow with the current setup. The likely issue is not so much as to running the equipment separately, but one caused by phosphates.

2 things that may help…

1. Maximize flow to the hot tub and the pool. Make sure the suction/return lines are adjusted so there’s adequate water movement in both bodies of water.

2. Use NoPhos or a comparable product to attack the phosphates and remove the food source of the algae.



fireyourpoolguy April 5, 2011 at 7:38 am

@ Betsy,

I can understand the frustration. This is a cyanuric acid (conditioner) issue. Once you top of the water add cyanuric acid to protect the chlorine. This will keep it protected from the sun to eliminate/reduce any algae issues (assuming the free chlorine is adequate).



Ian Poole April 5, 2011 at 9:09 am

I have been strugling with green tinted water for about 3 weeks my neighbours pool is crystal clear. Having put the normal amount of chlorine into the pull each week. I put Chlorine shock in and left it running for the day. Bingo crystal clear water again.


Polaris 280 April 3, 2012 at 1:15 pm

Maybe I missed it but I also turn my “Olga” loose on day one of the season to get the bottom cleaned up. “Olga” is my Polaris 280 automatic pool cleaner. It’s a real back-saver, friend and I can’t live/swim without her!


mike April 5, 2011 at 5:52 pm

I’ve been blessed by three consecutive swimming seasons of perfectly clear water. I attribute this to :
1) A high quality pool cover that lets water pass into the pool but does not permit any light tp penetrate.

2) On the very day that the cover is removed, clean filter cartridges a installed into the filter and the pool equipment is started as soon as the pump is primed.
3) I have an automated chlorine measurement and dispensing system that creates chlorine from salt water and uses Ozone to oxidize any remaining chlorine byproducts. All I need to measure on a weekly basis besides the normal tests is to measure the salinity.
4) My system measures the PH and adjusts it by adding CO2 as needed. I used 1/4 of a tank last season.
So far, either I’ve been lucky, or I’m doing the right things.


mgo April 5, 2011 at 7:23 pm

tried a new hth product.. ..called green to blue.. wal-mart($13.) as promised!


Anonymous June 10, 2011 at 6:45 pm

Green to Blue is only for sand filteration systems.


swimming pool pumps April 8, 2011 at 12:33 am

I read the information you provided regarding Green Swimming Pool Water. Thank you so much for making your research data available to us. If I ever buy a pool, I will know what to use to safely keep the pool clean.


Susie April 13, 2011 at 2:44 pm

Hey Terry, I have previously used your books to cure my green above-ground pool. This year we had thought our pool liner was going to have to be replaced since we had extensive leaking last summer, so we waited for the water to leak out over the winter (did not cover pool). The water level is high now (why??), so I decided to try to salvage the pool, but can’t turn my pump on until I get the debris out of the pool….I tried using my nets and hose with leaf basket to remove leaves but can’t even see the bottom. Is this worth pursuing, or would you advise draining the pool and starting over? It is REALLY green and murky this time…can it be saved?


Anonymous May 16, 2012 at 5:11 am

If your pool was leaking before and isn’t now, most likely it got plugged up by all the debris in the pool. So if the liner is in bad condition, I would suggest not wasting all the money trying to clean the water and just go ahead and replace your liner.


fireyourpoolguy April 14, 2011 at 9:29 am

Hi Susie,

Tough to say without knowing all the variables or how much debris is in the pool. Assuming it’s less than about 6k gallons, it’s likely a lot less expensive and time consuming to drain the water and start from scratch.



Bonnie B April 15, 2011 at 9:25 am

Thanks for your article! It’s always scary to pull off that cover for the first time in 6-months. It’s nice to know I can treat the water without calling someone.


Vanessa July 24, 2011 at 1:13 am

Hello Terry,

I am a manager of an apartment complex and recently I lost my maintenance man, As a result this has made me responsible for the pool. I know absolutely nothing about pools. I was absent from work for a week and upon my return I discovered that my pool had turned the color of a deep green,(Algae). I first tried to salvage the water before I had to drained the pool. After I drained the pool I had to take a shovel and shovel the algae out of the bottom of the pool. After I drained, scrubbed and refilled the pool with water, I turned the pump back on and as the water began to shoot out of the water jets inside the pool I noticed the water that was shooting into the pool was green. Therefore, my water is green again. Its not as green as it was in the beginning but I do have a light green tint. How do I rid my pool of the light green tint? HELP!!!!

Vanessa K


Art dec'eau July 26, 2011 at 3:40 am

Hi there, thanks for another great article. As a professional pool builder, we appreciate that our customers can get this kind of information, and solve this problem without having to call us first.


pool cleaning service August 11, 2011 at 9:40 pm

Hi there, thanks for another great article. As a professional pool builder, we appreciate that our customers can get this kind of information, and solve this problem without having to call us first.


Jen Allen January 6, 2012 at 9:38 am


Great website with practical information. Love it. Most of the time, it seems like pool companies and professionals are talking down to people, and it’s nice to find another like-minded person who just wants to educate!

I like how much emphasis you put on circulation and filtration. I believe the filter system is the heart and soul of any pool. If it’s not running, or not functioning properly, or dirty….you simply will NOT have beautiful water! We’re in different areas, so I think things may operate a little different, generally. It’s the common practice, in Iowa, to run your pump 24/7 ALL the time. A lot of times customers I work with who DO have green pools, or have a problem keeping them clear, either have not been circulating and filtering enough, OR they have a filter system that is not effective on their pool size.

Thanks again for your information. I’ll be directing my readers to your website for sure!

Jen Allen
Central Iowa Pool & Spa


hot tub filter cartridge February 6, 2012 at 8:59 pm

The blog is such a manual by which we get many good things and this is also a very useful writing.


Shasta Pools & Spas March 30, 2012 at 5:02 am

Indeed, having a pool as clean and clear as our drinking water is very ideal. But of course, our pool does not always stay clean, so it needs routine cleaning. The 4 steps above are useful for pool owners. Thanks for the post.


A Mother, who takes care the pool for her kids June 5, 2012 at 3:02 pm

Thanks gosh, I found this site … This is the first time ever we owned a saltwater pool & Spa. My husband travels a lot and I had to pay at least $40 per week for someone to take care of our pool. I finally decided to use what I watched and learned from the pool service person and take care of the pool myself so I can save those extra money to buy toys for my little girls. I have been done a great job last month. Last week, I had to drain the Spa for unexpected reason. I assumed that the pump or whatever it’s called will stop after the water is completely drained so I didn’t check back .. When I get home after a few hours, the pump was die … (I think it’s burned) .. oh well, my husband had to pay $400 to replace it. I refilled the water and now I found many green spots on the bottom of the pool and spa. I did exactly the same a month ago, but I think I am missing something here .. I put 3lbs of shock yesterday, the water is blue now, but not clear …. and the green spots are still there. What should I do next, please help !!! … is quality water clarifier something I can buy from the store ? my little girls swim everyday but I didn’t allow them for 3 days … Please help ASAP … if possible, I also would like to know how often I need to add salt and by how much …how oftern I shock the pool … I found out that the spa turns green quicker than the pool … PLEASE HELP !!!


michelle sonnenreich June 19, 2012 at 5:55 pm

I cannot remove the top part of my cartridge filter dome… Any tricks? I am step.2 unto turning my green pool blue, so far with success. I would like to clean the filter cartridge.


yvonne bliss July 25, 2012 at 9:53 pm

I started up new pool with recommended salt and cyanuric acid. Ran filter pump for 24 hours. Added a biodegradable clarifier. Ran pump filter another 12 hours. Noticed some murkyness and added allowed amount of hth super clarifier. Water looked ok at this time. I started the salt/chlorine generator. Within 3-4 hours my pool water looked a clear greenish. Not knowing i continued my required 9 hour electrolytic chlorinator process. When completed my water is now very green with a brownish slimy ring around the inside of my pool liner. Will your 4 step process work for this problem?
Yvonne Bliss


fireyourpoolguy July 26, 2012 at 10:17 am

Hi Yvonne,

Yes, the 4 steps will likely (I don’t know all the variables you’re experiencing) resolve what you’re experiencing, but also be sure to test for phosphates to ensure there isn’t another underlying issue taking place.


Terry Duff


Darline August 2, 2012 at 4:59 pm

I used HTH Green to Blue Shock System in my pool. I read the directions but didn’t understand what “vacuum to waste” meant and decided to figure it out later. I completed the steps and the water is no longer green but the sediment is at the bottom. It turns out that I have a cartridge filter not a sand system. HTH suggested that I empty to pool and start fresh. Since its late in the season I’d rather not do that. Any ideas?


fireyourpoolguy August 6, 2012 at 8:42 am

Hi Darlene – there’s likely no need to do a drain/refill. Vac to waste can only be done if you have a multi-port backwash valve (you’d know if you did, if you don’t have one, not the end of the world). If you don’t have this type of mechanism, do a regular vacuum, but do so with the filter in the backwash position – this will essentially remove the sediment from the pool and remove it from the pool (so it doesn’t re-enter via the return line as you’re vacuuming).

Hope this helps.



Johnson August 30, 2015 at 5:28 am

I do followed the poceedure,but am delling with fibra glass pool,I don’t know what I can do when many people swimming inside
it will change to green ,and cloud


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