Pool green just a few days after cleaning/shocking

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llang31ll

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Jun 21, 2012
22
Hi I really need some advice from an expert. I've been battling algae with my pool ever since I moved into this house. I clean it once a weak, vacuum, shock, chlorine, algaecide, etc. I've done a lot of research online and talked to some people and it seems like I'm doing the right thing but it just won't stay blue!! Today I am finally fed up because I just cleaned it 4 days ago and it is green again with these readings...
pH 7.8
FC 5
TA 180
stabilizer 150.
Filter system is being run 8 hours a day

I would think that with a higher FC than normal there would be no algae growth but somethin' bad is goin' on here. Also, the pool has been free of swimmers.
i appreciate any advice anyone can give me. Thank you.
 
Welcome to TFP!

You didn't actually kill all the algae. It is nearly impossible to maintain a pool when stabilizer/CYA is over 100, let alone get rid of algae. I strongly recommend that your replace water to get your CYA level down to something more reasonable, preferably between 50 and 60. Until you do that, it is going to be nearly impossible to resolve the algae issue.
 
JasonLion said:
Welcome to TFP!

You didn't actually kill all that algae. It is nearly impossible to maintain a pool when stabilizer/CYA is over 100, let alone get rid of algae. I strongly recommend that your replace water to get your CYA level down to something more reasonable, preferably between 50 and 60. Until you do that, it is going to be nearly impossible to resolve the algae issue.
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Hi Jason! I sincerely appreciate your speedy reply. In order to decrease CYA I have to drain the entire pool, refill it, and start over? Do you know how CYA became so elevated in the first place (so I can avoid that next time around)?

Thank you!!!!!
 
No, you do not have to drain the entire pool. To go from 150 ppm CYA to 50 CYA you need to replace 2/3 of your water. What kind of a pool surface do you have? Vinyl? If it is vinyl you cannot drain your pool down very far without risking the liner pulling away or wrinkling. You will have to do it in steps. Also, how do you know your CYA level is 150? Pool store? They are notoriously bad at testing high CYA levels. Your level could be even higher. If you want to take control of your pool, read the Pool School link above right and order yourself a good test kit. I use the TF-100--top of the line.
 
MattB said:
No, you do not have to drain the entire pool. To go from 150 ppm CYA to 50 CYA you need to replace 2/3 of your water. What kind of a pool surface do you have? Vinyl? If it is vinyl you cannot drain your pool down very far without risking the liner pulling away or wrinkling. You will have to do it in steps. Also, how do you know your CYA level is 150? Pool store? They are notoriously bad at testing high CYA levels. Your level could be even higher. If you want to take control of your pool, read the Pool School link above right and order yourself a good test kit. I use the TF-100--top of the line.
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I use a test strip- CYA is the same as ppm (ppm) right?
 
CYA is cyanuric acid, also known as stabilizer. It is measured in parts per million, abbreviated as ppm. All pool level tests are reported in ppm--except for pH. As for the CYA test strips, I have never used them and don't know anything about their accuracy.
 
CYA is measured in ppm but you may not be getting accurate test results from test strips.

The suggestion to replace your water is based on the 150 ppm CYA. CYA is also called "Stabilizer". It is used in pools to stabilize the chlorine against the effects of the sun. The chlorine is there to sanitize the water and kill off the algae and other bacteria. The problem is CYA decreases the effectiveness of the chlorine.

If you had no CYA in the pool, you need about 5 ppm of chlorine to keep it clean and clear (and not green). For a 10,000 gallon pools, that is about one half a gallon oz of 10% chlorine.
With your CYA of 150 and green water, you would need about 33 PPM to kill the algae and to get there will require at least 3.2 gallons of the same 10% chlorine... and then you need to keep it at 33 PPM until the water is clear and you stop losing chlorine to the algae.

I suggest you read the Pool School while you drain the pool to about 4 inches of water and refill the pool You will be much happier in the long run and likely to be done in a few days.
 
llang31ll said:
Thank you everyone! It looks like I have a lot of reading to do. Pool School Rocks
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It does indeed. Honestly, the vast vast majority of all pool water problems are corrected with Pool School and a good test kit. The odds are very good that your pool chemistry isn't special or unique and you will be in charge of your pool in no time. :)
 
Ok so I figured out why my CYA reading is so high- 10 years of using chlorine tablets usually 3-5 at a time. I gather that at this point I should:
1. Scrub algae off walls and floor
2. Drain pool by ~90%
3. Refill
4. Add Cyanuric Acid (Stabilizer) to ~30ppm
5. Switch to a non-stabilized chlorine from now on

How does this sound? Please let me know if I am missing something. Thank you all! :-D :-D
 

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You are a quick study!

How much sun do you get on your pool? If you get a lot during the day, you will want to eventually be closer to 50 ppm CYA. But if you want to start at 30 ppm that is good too, especially since you are going to probably want to shock your pool after you refill. You have algae that you need to make sure is dead, even after a water replacement. And having a lower CYA level means a lower shock level (i.e. less chlorine), as I'm sure you read about in Pool School. :-D

Good plan! If it were me, I would only add bringing my pool through the shock process after refilling to ensure all the algae is dead.

One more thing: make sure it is safe to drain your pool way down that far! You never said what kind of a surface you have.
 
MattB said:
You are a quick study!

How much sun do you get on your pool? If you get a lot during the day, you will want to eventually be closer to 50 ppm CYA. But if you want to start at 30 ppm that is good too, especially since you are going to probably want to shock your pool after you refill. You have algae that you need to make sure is dead, even after a water replacement. And having a lower CYA level means a lower shock level (i.e. less chlorine), as I'm sure you read about in Pool School. :-D

Good plan! If it were me, I would only add bringing my pool through the shock process after refilling to ensure all the algae is dead.

One more thing: make sure it is safe to drain your pool way down that far! You never said what kind of a surface you have.
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Thanks Matt!
My pool sees sun from rise to set- I will shock it and bring it to 50ppm as per your advice :-D
Should I shock after draining and before refilling since presumably all the algae will be scrubbed off the walls and on the floor in whatever water is left so I can use less shock because I'd have a smaller amount of water?

so this 'lower CYA = lower shock = less chlorine' thing... naive question for ya- does this mean i should always measure CYA first and then somehow determine how much chlorine I need and then somehow measure that before I put the chlorine in? Rather than just add the chlorine based on instructions on the label.

As far as draining goes. It was done by a professional when I first bought the house because the pool was basically a swamp. I've never done it myself and honestly don't know what kind of surface I have. It might be plaster? I'm not really sure of all the differences... google won't give me pictures of the different types! I can tell you it's white, feels roughish, and when there are pieces that break off they become chalky. Any idea what this description is?
I think I'm going to do the draining myself this time..Any suggestions?
 
You have a plaster pool. I have no experience with draining/refilling plaster pools. One of the experts here will chime in tomorrow about draining/refilling plaster. I'm pretty sure chunks of it shouldn't be breaking off. :shock:

As for the shocking process, do it AFTER you have completed all of your water replacement and refilled your pool. Then measure your CYA level to make sure it is down between 30 and 50. Once you have your CYA level, you can then determine your free chlorine (FC) shock level from this chart: pool-school/chlorine_cya_chart_shock (Note how the FC shock level is lower for lower values of CYA). Then go through the shocking process as described here: pool-school/shocking_your_pool. You are finished shocking when you have passed the OCLT described here: pool-school/overnight_fc_test

Also, you need to get familiar with the Pool Calculator so you know how much liquid chlorine/bleach to add during the shock process: http://www.poolcalculator.com/

Have fun! Keep posting questions if you have them!
 
MattB said:
You have a plaster pool. I have no experience with draining/refilling plaster pools. One of the experts here will chime in tomorrow about draining/refilling plaster. I'm pretty sure chunks of it shouldn't be breaking off. :shock:

As for the shocking process, do it AFTER you have completed all of your water replacement and refilled your pool. Then measure your CYA level to make sure it is down between 30 and 50. Once you have your CYA level, you can then determine your free chlorine (FC) shock level from this chart: pool-school/chlorine_cya_chart_shock (Note how the FC shock level is lower for lower values of CYA). Then go through the shocking process as described here: pool-school/shocking_your_pool. You are finished shocking when you have passed the OCLT described here: pool-school/overnight_fc_test

Also, you need to get familiar with the Pool Calculator so you know how much liquid chlorine/bleach to add during the shock process: http://www.poolcalculator.com/

Have fun! Keep posting questions if you have them!
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Thank you for all the resources...You are very helpful!
After researching 'how to drain and refill pool' I am now freaking out about the water table and hydrostatic pressure and don't want my pool to pop in!! I know draining has been done before and my pool lived so I think it'll be okay...but I may have to call in a professional company just to feel more confident.
I guess the plaster is breaking off from years of sun light.. it just leaves divots on the pool surface, is that a bad thing?
 
llang31ll said:
Thank you for all the resources...You are very helpful!
After researching 'how to drain and refill pool' I am now freaking out about the water table and hydrostatic pressure and don't want my pool to pop in!! I know draining has been done before and my pool lived so I think it'll be okay...but I may have to call in a professional company just to feel more confident.
I guess the plaster is breaking off from years of sun light.. it just leaves divots on the pool surface, is that a bad thing?
Click to expand...

I'm sorry I can't give you any advice regarding draining/refilling/hydrostatic pressure/cave-in because it is something I would be less than calm about too. :pale:

Also, hunks of plaster coming off leaving divots can't be a good thing at all. Yes, it might be time to call in a professional. As long as you are draining, you might as well have somebody look at your surface. At the very least you could post some pictures here and one of the many experts here would be able to tell you right away what kind of a situation you are in.
 
You don't want to drain below the local water table depth. If you live in a wet/swampy area that can be fairly high and if you live in a dry arid climate it can be extremely low (way below the bottom of the pool). If you have no idea what the water table depth is, I would only drain about half way down.
 
Hi, welcome to TFP! Go ahead and drain about 1/2 the water, refill then test. We recommend a high quality test kit such as the TF100. The TF 100 will allow you to test the higher chlorine levels needed to complete the shock process and the tests produce accurate, consistent results. Once you have refilled, post your test results here and we will help you determine the next step. You may need to drain 50% and refill again and you may not. Test results will let us know what is needed. If you have not received a good test kit (FAS-DPD kit) you can take a sample to the pool store and have them test for you. Just don't buy anything! (Unless it is liquid chlorine!)
 
I did nothing yet but just retested out of curiosity and got CYA of 100 this time- consistent over 3 tests. I know the test strips are inaccurate and I will take your Zea3's advice and bring a sample to the pool store to confirm before I do anything, but i'm just thinking ahead... with only FC and TA high would drain+refill be necessary? and would would cause an elevation in FC and TA only?
 
If you want, you could re-test your CYA using half pool water and half tap instead of all pool water. Instead of using 50% reagent and 50% pool water for the test, you do the drop test using 50% reagent mixed with 25% pool and 25% tap water. You then double your test results. If your CYA test comes in at 50 ppm, you really have 100 ppm. If it tests as 75 ppm, you have 150 ppm.

The CYA test is less accurate if your CYA is over 100 PPM and it may only read as 100, when it is really 150 or more.
 

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