Confused - levels seem right though pool is green

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andyjames

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Aug 13, 2016
45
Ellicott City, MD
Hello - we are new pool owners and have been struggling with keeping the water clear...it seems to get out of balance and turns green really quickly. We have been juggling the pool store and blogs and just can't figure it out. As an example, we have started using a test kit - and yesterday everything seemed in a good range yet this morning the pool was a little green... I just went and tested the water again, it's even more green, and got these numbers:

Cl - 3 ppm
Br - 6 ppm
Ph - 7.5
Total chlorine - 5
TA - 160

Total alkalinity seems high though is there a reason the pool is green (i.e. does that prevent the chlorine from working or something?!). It seems we need to lower the TA with muriatic acid - though is that all...and what else are we doing wrong!? it's about a 30,000 gallon pool (a little more), plaster (that the previous owners actually painted themselves so paint chips are coming off...)...pretty shaded area for half of the day (different types of trees) any advice is very much appreciated.

Thank you
 
Welcome to TFP!

You're missing the most important number to see if your numbers are "good" or not: CYA

What testing kit are you using? Without a good read of the amount of Cyanuric Acid, we're not going to be able to tell what level your chlorine needs to be at. Now, since you're likely dealing with an algae breakout, we're going to ignore everything but ph. Once you have your CYA reading, post here and we can help you further. In order to clear up this pool, though, you're going to need an approved testing kit - once we know how you're currently testing, we can help you with that as well.

Finally, please put your pool details in your forum signature. This information will also assist us in getting you back to a clear, sparkly pool.
 
I'm not familiar with the K-1004, but if all you're missing is the CYA test, the HTH 6-way test at Wal Mart includes one.









You also need a FAS-DPD chlorine test to follow the TFP method, and that's included in either the K-2006 or TF-100. But since you'll need to order one of those online, that HTH kit will at least allow us to determine what your FC target needs to be right now.





If your CYA is 100 or above, your minimum FC needs to be at least 7 to prevent algae and optimally should be 11. Since you're reading only 3 and have algae, it's likely your CYA is way too high. The is the result of using tablets or other dry forms of chlorine to chlorinate your pool. Most of these add CYA, which can only be removed by draining and refilling. The higher your CYA level, the higher your FC needs to be, as CYA binds to chlorine and lessens its effectiveness.

You should only use liquid chlorine, aka. bleach, to add chlorine to your pool, as it does not add any CYA.
 
andyjames said:
We are using Taylor K-1004, no CYA test. What should we get?
Click to expand...

Does it look like this: Amazon.com : Taylor Troubleshooter DPD Pool and Spa Water Test Kit - K-1004-6 : Swimming Pool Liquid Test Kits : Patio, Lawn Garden

If so, you can do a TA test, and basic chlorine DPD test, which will not go high enough for your to properly clear up your pool.

So, you'll need a FAS-DPD test: TFTestkits-FAS/DPD
A CYA Test: TFTestkits-CYA

And if you have an in-ground, plaster/pebbletec pool, a CH test: TFTestkits-R0010 and TFTestkits-R0011L and TFTestkits-R0012.

If you need all of these, seriously consider just getting a TF-100. I know it's a little pricey, but you'll save more than the cost of the kit in not buying random algaecides, phos-free, and other pool-store elixers that will do nothing to clear up your pool and fix your problem (in fact, a lot of it will make your problem WORSE).
 
Sounds like you are in a confusing situation. Looking for advice in numerous places - getting lots of seemingly conflicting ideas.

I'll answer the 2 questions from your post :

Why is my pool turning green? - Your pool doesn't have enough chlorine in it. It is as simple as that.

Is your hi TA important right now? - No. Right now TA doesn't matter at all.


For reasons I cannot begin to explain virtually the entire pool industry ignores the relationship between Chlorine levels and CYA. CYA binds to "chlorine" and protects it from sunlight - slowly releasing it back into the pool. Unfortunately CYA also protects the Algae from the chlorine. If your CYA to Chlorine ratio is wrong algae can grow in the pool even though your chlorine levels as "correct"

Take some time and read through Pool School. Most of us came here in your situation - confused, stressed, green pool, etc. - I certainly did. My pool has been Trouble Free for many years now - yours can be too.
 
AndyJames, welcome to TFP.

I just want to add that the most common cause of green is organics, as lightning guy pointed out, and that if your cya is high, your FC is too low to preven organics.

But, just so you know, if your on well water that contains iron, or if a large volume of copper-containing algaecide was used, it would then be possible that the green is from oxidized metals -- in that case, the green is usually crystal clear but tinted and would have turned "immediately" on having added chlorine.

So let us know if you have any reason to suspect metals in your water, because the plan going forward changes in that case.

One test you can likely do if your FC test is the drop-type while you're waiting fr an upgrade/addition to your kit to arrive is the Overnight Chlorine Loss Test -- if you lose chlorine overnight when the sun is down, its a sure sign something's consuming your chlorine and that you need a SLAM Process. Read up on that process as I suspect once your cya is confirmed, you will need to do so. One cannot do a slam without knowing the cya -- keeping the [fc/cya][/fc/cya] to the slam level is what makes it work.


So, if you lose chlorine overnight, then its almost definitely a case of algae...but if you don't lose any FC overnight AND you're on well water that has iron, you would instead try a metal sequestrant if you were sure you didn't need to slam. Either way, need to know your cya.

Make sense?
 

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Thank you all for your input/advice. We will definitely look to get a better test kit - though the numbers we have from the pool store yesterday afternoon are:
Free Chl - 3.58
Total Chl - 3.6
CYA - 80
pH - 8.1
Hardness - 251
TA - 122

I put in 2/3 gallon of Muriatic Acid last night to lower the pH... The pool is even more green today and I just tested it again with our current kit: Chl = 3-ish; Br = 6-ish; pH looks to be about 7.5 or so; and TA is about 140-150...

Are we still looking at just needing more chlorine to kill the algae? even though the tests say the chlorine is a bit high?

Thanks!!!!
 
Hi AndyJames,

As someone who's relatively new to pools and just started taking care of my new pool myself this year, let me just say this is kind a lot to get your head around at once but folks here are helpful so just stick with it. After the pool store clouded my water telling me I could add CA & Cl at the same time, which wasn't fatal but annoying, I quit listening to them completely and my water sparkles and I have no algae problems even in tx heat. This is why they're telling you basically "who you going to believe?". I assume the pool store is the one telling you your FC is ok. But, if you go back looking through this site at the recommended levels, and the pool school information it will tell you with a CYA of 80 your FC should be maintained at a minimum of 6, up to 9. As you read through the comments several have said you need more chlorine. and this is why they're telling you to find out your CYA. I still go in the pool store occasionally for parts or oddities but I never, ever let them test my water or tell me what to get. And my pool looks great. We had my grandson's 6th birthday party in it recently and the water felt great! Everyone commented how clean it was. :)

Here's a direct link to the chart-I didn't stumble on it easily when I was first on the site. Good luck!

Pool School - Chlorine / CYA Chart
 
Thank you again - okay, so now I have better understanding of the relationship between CYA and chlorine...do I just then plug in my current level and target level and add bleach/chlorine to get it there or do I need to shock it and get rid of the algae to start?

Also, is there an optimal CYA level? i.e. should we aim to lower that - so chlorine levels don't need to be so high...?

A quick note - I just went to the pool store to get the water tested since we don't have the right kit here...though it is a bit confusing as to why the computer they use knows the CYA and recommends chlorine to be 3 (not 9, based on the TFP table)...
 
The chemical that actually sanitizes your pool is hypochlorous acid (HOCL) - this is what we call "chlorine". HOCL is a strong oxidizer and kills algae and bacteria very effectively. Once HOCL does it's thing it converts to chloride salt (table salt).

CYA binds with HOCL and takes it out of the solution. This is a good thing as CYA protects the chlorine from sunlight - but too much CYA and algae can grow in the pool even with FC levels of 3 or 4.

You always want 0.07ppm of HOCL in your pool to prevent algae growth.

At 80ppm CYA and 4ppm FC you have somewhere around 0.02ppm HOCL in the pool. This is your problem. Way too little HOCL.

Everything you'll read about chlorine and algae here at TFP has to do with this relationship with HOCL and CYA.


You are gonna need to choose whose advice to take here. Your friends at the pool store will have you running around in circles - that I promise you. For whatever reason the pool industry doesn't recognize the science behind CYA and Chlorine. The EPA says 3ppm FC in your drinking water - and that's all you will hear.
 
Welcome to TFP Andyjames

I'm sure your head is spinning. Everything we teach is based on accurate testing of your water. Please take some time to read these links.

Pool School - Test Kits Compared
Pool School - ABCs of Pool Water Chemistry
Pool School - Chlorine / CYA Chart
Pool School - SLAM - Shock Level And Maintain

If your water is green due to algae, simply maintaining chlorine will not kill it. You will need to follow the SLAM process where you keep your chlorine at shock level for your CYA until you pass the three tests in the article. If you don't follow this process the algae is reproducing faster than your chlorine is killing it.
 
Thank you AimeeH - yes, head spinning...so, the question now is whether we SLAM with bleach (our CYA was 80 - so we need to bring CH to 31 based on the chart, right?)...it's like 15-16 jugs of bleach - or just use a shock solution from a store/on-line? it seems adding the powder will continue to increase our CYA so bleach is preferred (?) though how quickly do we add the bleach?

Also, our CC is .02 and our FC is 3.5...

Thanks!!!!
 
FC (free chlorine) of 31.....yes. Not CH. CH is calcium hardness.

"Shock" products are also chlorine (just like bleach) but all dry forms of chlorine are stabilized by either calcium (cal-hypo) or CYA (di-chlor and trichlor).

Which is why we reccomend liquid chlorine. It doesn't add any of the other byproducts mentioned above. There may be a place and time for any of those but until you fully grasp the ABC's of that chemistry, we'd reccomend liquid chlorine/bleach.
 
Go ahead and pour in what you need. Keep pump running. And you'll be well served to brush after adding. I add it in front of two jets on a swimout bench. You'll want to add slowly in front of a return to disburse it. But brushing is important too.
 
Going to be really hard to SLAM without the correct test kit to accurately measure the high levels of FC.

I think I would get the proper test kit ordered and delivered before you even get started.

While waiting for the kit, I would work on doing a 50% water change and get that CYA level down to a more manageable level. You can do a few partial changes if you have a high water table or cannot lower the pool level that far. This will help a lot and save you a ton of bleach. You will probably have a very hard time even getting to 31ppm FC, get that CYA level down to around 40 and you will have a much better go of this.

That's where I would start,

In a pool that large you should add a couple gallons of bleach each day just to keep things from getting worse. Remember bleach or liquid pool shock only! Get that kit ordered right away, the sooner the better. You could order a K-2006 from Amazon and possibly have it quicker. This is essentially the same kit but not quite as many reagents as the TF-100. You simply cannot rely on pool store testing or the kit you have, you cannot accurately measure chlorine levels that high.
 

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