Spots of algae even with chlorine 1-3

[Ekn2484]

Hello all. I am about an 18,000 rectangular pool. New home owner that came with the pool. After getting over a major algae problem and getting the pool in the shape, I still get areas of algae on the bottom and sides each day even though free chlorine 1-3. I test with the Taylor kit. pH has been good 7.5-7.8. I just tested CYA and it was high around 80.

Is the CYA too high for chlorine to be effective? At this point, I’m adding between 5-14 oz chlorine per day and it seems like I’m chasing the algae and never getting on top of it. I use Leslie’s granular chlorine (maybe not the best product?) and then I scrub the pool most days.

Pool filter is working well. Service company came out to take a look.

And recs?

 

[Newdude]

And recs?

Stay free and clear of min FC per your CYA level, at all times.



Have some reading :
Pool Care Basics
FC/CYA Levels

To clear the algae : SLAM Process

And Welcome to TFP !!!

 

[reggiehammond]

Which test kit? Test Kits Compared
Algae is caused by insufficient chlorine. Has nothing to do with filtration, etc.

Do you have a salt water chlorine generator? If not, your CYA is pretty high.
Chlorine is only stabilized into a dry form by two methods; binding to CYA or binding to Calcium.

Using dry chlorine products will get you quickly to having too much CYA or Calcium quickly.

TFP teaches a much easier, simpler, cheaper method of pool care.
Pool Care Basics

 

[Ekn2484]

Thanks so much. So I should use liquid rather than solid chlorine. And no don’t have a SWG. Will the CYA gradually go down over time or do I need to drain some water? And is there a particular liquid chlorine product you’d recommend? What about chlorine tabs? Good or no?

 

[JJ_Tex]

Thanks so much. So I should use liquid rather than solid chlorine. And no don’t have a SWG. Will the CYA gradually go down over time or do I need to drain some water? And is there a particular liquid chlorine product you’d recommend? What about chlorine tabs? Good or no?

Liquid chlorine is the best as it only adds chlorine. Tabs and powders add CYA or Calcium depending on the formulation and will build up in your water. In our area, Walmart is the best place for liquid chlorine. Christmas is here (in the eyes of retailers) so stock up soon before the pool aisle turns into inflatable snowmen and blinking Christmas lights.

Pinch a penny is good too with their refillable jugs.

 

[reggiehammond]

Thanks so much. So I should use liquid rather than solid chlorine. And no don’t have a SWG. Will the CYA gradually go down over time or do I need to drain some water? And is there a particular liquid chlorine product you’d recommend? What about chlorine tabs? Good or no?

I would not own a pool in DFW without a salt water chlorine generator. Liquid chlorine is expensive and annoying to source throughout our long swim seasons. Dry chlorine will require frequent drains and refills or you'll end up with algae or scale. CYA does degrade over time and with heat, but if you using dry chlorine with CYA, it won't degrade fast enough.

 

[Ekn2484]

still having problems with algae despite chlorine levels consistently above 3-5. Is that normal? I will scrub the pool and the next day, the bottom is dusty and with a layer of algae. It’s not normal to consistently have a dirty bottom of a pool, right?

 

[sande005]

You need to go back and read NewDude's post again, INCLUDING all the links in it.

Review the chart he posted. If your CYA is still 80, you have been way, way under chlorinating your pool. You normally at that CYA level should be in the 9-11 range.
Since you have algae, the only way to get rid of it is with lots of Cl over many days - the SLAM method. Read up on it, there are details you must know before doing it. With CYA at 80, getting your Cl up to a level of 31 is very hard to do, and to maintain. It will cost a LOT in liquid chlorine.
You should replace about 1/2 of your pool water to get the CYA down to a more manageable level, then you can start the SLAM process. It will still take days and days. With lots of scrubbing and filter cleanings.
Only ever use liquid chlorine. It is the powders (and tablets, if you used any) that got you into the CYA problem. And being way too low on the Cl level got you into the algae problem.

 

[TinFoilHat]

You need to SLAM with a proper test kit such as Taylor K2006C or TF Testkits TF100 or the preferred TFPro. Stock up on liquid chlorine because you'll be using a lot of it.

 

[JJ_Tex]

still having problems with algae despite chlorine levels consistently above 3-5. Is that normal? I will scrub the pool and the next day, the bottom is dusty and with a layer of algae. It’s not normal to consistently have a dirty bottom of a pool, right?

Right. FC of 3-5 is too low for your CYA. Forget what Leslie's and others say, your chlorine level should be based on your CYA, not some blanket statement of 3-5 based on 1960's understanding of pool chemistry.

Look at this chart showing your Target FC range that I made (the official TFP link to the FC/CYA ratio is in my signature). For your CYA of 80, which is very high, your FC should be 9-11 and never ever ever below 6. That is why you are getting algae. I've followed this chart since day 1 of my pool and never had a speck of algae in my pool, no chlorine smells, no red eyes, etc.

 

[Ekn2484]

Oh interesting. But I guess I should get liquid chlorine to make chlorine higher since adding granular chlorine will continue to raise CYA? Is that right?

 

[JJ_Tex]

Oh interesting. But I guess I should get liquid chlorine to make chlorine higher since adding granular chlorine will continue to raise CYA? Is that right?

Yes. Liquid chlorine adds only chlorine.

Granular either adds CYA or Calcium, look on the packaging to figure out which you have.

• Trichlor - adds CYA. This is most commonly found in pucks, but there are also some powdered shocks
• Cal-hypo - adds Calcium. This is most commonly found in powdered shocks, but some pucks can be Cal-hypo and usually advertised that they will not add CYA

 

[Ekn2484]

You need to go back and read NewDude's post again, INCLUDING all the links in it.

Review the chart he posted. If your CYA is still 80, you have been way, way under chlorinating your pool. You normally at that CYA level should be in the 9-11 range.
Since you have algae, the only way to get rid of it is with lots of Cl over many days - the SLAM method. Read up on it, there are details you must know before doing it. With CYA at 80, getting your Cl up to a level of 31 is very hard to do, and to maintain. It will cost a LOT in liquid chlorine.
You should replace about 1/2 of your pool water to get the CYA down to a more manageable level, then you can start the SLAM process. It will still take days and days. With lots of scrubbing and filter cleanings.
Only ever use liquid chlorine. It is the powders (and tablets, if you used any) that got you into the CYA problem. And being way too low on the Cl level got you into the algae problem.

Thanks. That’s very helpful! will see about replacing the water and getting liquid chlorine

 

[Ekn2484]

Yes. Liquid chlorine adds only chlorine.

Granular either adds CYA or Calcium, look on the packaging to figure out which you have.

• Trichlor - adds CYA. This is most commonly found in pucks, but there are also some powdered shocks
• Cal-hypo - adds Calcium. This is most commonly found in powdered shocks, but some pucks can be Cal-hypo and usually advertised that they will not add CYA

Yeah mine is calcium hypochlorite. So reason that CYA is so high then?

 

[sande005]

Yes, to the liquid Cl question.
And for the first dose, if you don't lower your CYA, it will take 5 gallons. Then you retest after 2-4 hrs, and dose again to get back to 31. The amounts for those subsequent doses vary a lot depending on season, weather, and the overall amount of algae and most importantly your test results at the time. I wouldn't be surprised at several gallons per day. Depending on the conditions, it will take days, or in bad cases, weeks, of doing this to get rid of it all.
Cutting your CYA in half by replacing 1/2 your water will essentially cut the amount of liquid Cl needed roughly in half. While it won't replace 1/2 of your algae, it will reduce the population some, also shortening the time you need to be doing the SLAM.

 

[Ekn2484]

Yes, to the liquid Cl question.
And for the first dose, if you don't lower your CYA, it will take 5 gallons. Then you retest after 2-4 hrs, and dose again to get back to 31. The amounts for those subsequent doses vary a lot depending on season, weather, and the overall amount of algae and most importantly your test results at the time. I wouldn't be surprised at several gallons per day. Depending on the conditions, it will take days, or in bad cases, weeks, of doing this to get rid of it all.
Cutting your CYA in half by replacing 1/2 your water will essentially cut the amount of liquid Cl needed roughly in half. While it won't replace 1/2 of your algae, it will reduce the population some, also shortening the time you need to be doing the SLAM.

That’s very helpful! Makes sense. Yeah need to get rid of this algae! Okay will look into emptying half the water and then getting liquid chlorine. But any thought as to why CYA got so high with my calcium
Hypochlorite granular shock? Want to make sure that doesn’t happen again.

 

[JJ_Tex]

That’s very helpful! Makes sense. Yeah need to get rid of this algae! Okay will look into emptying half the water and then getting liquid chlorine. But any thought as to why CYA got so high with my calcium
Hypochlorite granular shock? Want to make sure that doesn’t happen again.

CYA only gets in the water from adding it. You can add it directly to the water in the form of "Chlorine Stabilizer", or it gets there by adding a product containing CYA including chlorine pucks. I assume you have been using pucks in addition to your granular chlorine shock?

 

[Ekn2484]

CYA only gets in the water from adding it. You can add it directly to the water in the form of "Chlorine Stabilizer", or it gets there by adding a product containing CYA including chlorine pucks. I assume you have been using pucks in addition to your granular chlorine shock?

No just the shock, myriatic acid, and alkalinizer. Maybe one of those has it?

 

[reggiehammond]

No just the shock, myriatic acid, and alkalinizer. Maybe one of those has it?

What is "alkalinizer?"

CYA is only typically added by use of chlorine pucks or by adding stabilizer directly to pool.

Before you do anything drastic, what specific test kit do you have? We need to be sure your results are accurate to avoid wasting time or $$.
It sounds like a good drain and refill might be beneficial.

 

[Ekn2484]

Thanks for everyone’s feedback. We drained the pool and now things are looking good. Question: with an ~17,000 gallon chlorine pool, how much liquid chlorine would you expect to go through per week? I have been adding close to a gallon a day (I have 10% chlorine, didn’t see the 12% at Walmart when I was there, the 10% is $5.67 per gallon), with chlorine 3-5 and then a day later, it’s virtually zero. I use the Taylor test kit. Wondering what is normal.