Why did I get algae?

[mgianzero]

My understanding is that if you keep tight pool chemistry (i.e. "balanced water") and keep your pool pretty clean, your pool should not produce much (if any) algae formation. I just bought an elaborate DPD test kit because I was getting some algae again. I have a SWG on a 24,000 gallon "pebble-tek" pool + spa with a DE-60 SF filter and 2-speed pump.
Here are my numbers:
FC: 5+ ppm
CC: 0 ppm
pH: 7.7
TA: 90 ppm
Calcium hardness: 280 ppm
CYA: 35 ppm
Phosphates: 100 ppm

My SWG reads 2700 ppm (although it tested at 3000 ppm at the local pool shop)

The temperature out here in sunny Cal is around 75-85 degrees (pool H2O around 78 degrees) and has been around that temp (70+ days and 60's at night) for about a month with very little ran, wind, etc. I took apart my DE filter a week ago and cleaned and replace all DE. I turn over my water about 1 volume/day which I have always been doing.

I now noticed (about 4-5 days ago) some algae on the east side (sunny-side) of pool. I believe it is green algae and not mustard since it has a greenish hue and sticks primarily to the walls and sides of the seats that face the sun. It sweeps easily with a brush and has no feel (not slimy or gritty, but I do have a pebble coating which may affect the way it feels).

My questions are ...

1) Why did I get algae if all my chemistry is mostly in check? (Maybe I could raise my CYA a bit and lower my pH and chlorine, but my pool chemistry doesn't look bad.) Could it be a circulation problem? I thought algae is mostly influenced by sun, rain, and low chlorine levels and/or phosphates. Does a recent DE cleaning affect this?

2) What algae am I getting? Is it green? What's my best way to get rid of it? Shock it with di-chlor or tri-chlor?

 

[frustratedpoolmom]

Hi, there...

What kind exactly is your kit? Taylor or other-where did you purchase? When you say DPD kit, do you know the specific number of your kit? If it does not include the FAS-DPD test, you really should supplement the kit you have with this FAS-DPD test.

Are these numbers your results, or the pool stores? If they are your results (which are probably more accurate than a pool store) :

Read about recommended levels in Pool School - your CYA is too low for an SWG.

For the algae to take hold, at some point the FC was allowed to drop. You will need to shock, and you should normally use Liquid Chlorine to do that. You can use the Pool Store liquid chlorine which is usually 10-12.5% or Clorox bleach (or the store brand equivalent) which is 6%. Either will work, shop around for the best price.

If you choose to use Dichlor (granular shock) that would be okay for now because your CYA is too low. Dichlor raises CYA levels. Regular use would not be recommended because of this, but since you need the CYA to go up anyway it would be okay.

So long as the PH doesn't go above 7.8 you should be fine, if it does, you need to lower it with Muratic Acid.

Phosphates really mean nothing, if you have proper chlorine levels it won't matter.

So read about Shocking your pool in Pool School, while your pool is at shock level be sure to brush the areas where you are seeing algae.

When you say one turnover, on what speed, how many total hours? It could very well be a circulation issue, consider running your pump on low 24/7. That works very well, and the low speed saves on electricity. I have run my pump on low 24/7 - going on 8 seasons now. Pump works great and I have never had algae while the pump was operating.

FYI - The Aquacheck salt test strips are the recommended way of testing salt levels, I wouldn't necessarily rely on the unit or the pool store...

Hope this helps! :-D

 

[frustratedpoolmom]

One more thing, you should update your profile to include your pool equipment/specs in your sig.

Go to User Control Panel - top left- then Profile - then Edit Signature. You are allowed 5 lines of text.

 

[mgianzero]

Okay, in response to your comments:

1) I have a standard DPD test kit from Taylor. I am not sure the kit #. Where's the number? I have 12 reagents bottles where I can test for chlorine, pH, TA, Calcium hardness, TCA. I really see no reason for a FAS-DPD test kit since this includes most everything I need. I know it measure CC directly, but is it really necessary. My CC was really zero since there was no change in color with R-0003. Isn't this accurate enough?

2) These results are mine, but very similar to the pool store's measurements. The only thing I could not measure was salinity except for reading it on my Aquarite system. (It read 2700 and I added a 40# bag which should raise it another 300 ppm to 3000 ppm).

3) With all due respect, my chlorine level has always been very high (3+-5+). Before my new kit I could only measure TC. But repeated visits to 2 different pool stores confirmed my FC was b/w 3+ and 5+. It hasn't been read low for quite some time (maybe 8 mos-1 year if even that).

4) I will raise my CYA. The Taylor book says to use a range of 30-50 ppm according to the National Swimming Pool Foundation Handbook of Water Chemistry and also ANSI/APSP. Does this standard change with SWG? Because they make no mention of this in the book. I will shock with 10 lbs of dichlor since I already have this and I need to raise my CYA anyways. Then I'll remeasure my TCA in a few days.

3) My pH has been a bit high (maybe as high as 7.8 but mostly around 7.6). I usually always have to add muriatic acid to bring it down. Maybe a pint or 2 at a time.

4) Regarding my turnover, I run my pool on high speed for 1 hour (enough to skim the surface and the spa spill over). This is around 105-110 GPM according to my flowmeter. (I know it's high flow, but that's because just re-plumbed my system and it flows much better now. Then I run my pool circulation on lo-speed for 7 hours (this measures at 50 GPM). That's more than one turnover per day.

5) This leads me to my real pressing question ... why did I get algae and what type is it? Taylor's manual talks about "breakpoint chlorination" or superchlorination to destroy high levels of combined chlorine, but my CC read zero according to my kit and the pool store.

FYI - Here's a picture of my pool:

 

[chem geek]

Do the pool sides with the green feel slimy? If not, then maybe it's some sort of staining (such as copper, though I don't know where that would come from) and not algae. Also, have you noticed any unusual increase in chlorine demand? The presence of algae usually results in an increase in chlorine demand so check the overnight drop in FC with the SWG turned off.

Usually, green algae is free-floating, but there are all kinds of algae so it's possible you've got something unusual that sticks to the sides and is more resistant to chlorine, though I believe that's a first that we've heard about.

 

[PaulR]

I really see no reason for a FAS-DPD test kit since this includes most everything I need. I know it measure CC directly, but is it really necessary. My CC was really zero since there was no change in color with R-0003. Isn't this accurate enough?

On this forum the standard recommendation is FAS-DPD, because it can measure a wide range (up to 50) to a resolution of 0.5ppm, and can be used for a resolution of 0.2ppm (although why you'd want to is beyond me). Also there's really no judgement call with FAS-DPD; it's just "is the pink all gone yet?" and counting drops same as the TA and CH tests.

The DPD test tops out at 5, if yours is like the one I inherited from the previous owner of my house; this makes it a problem to be in control of FC at shock levels that are much higher than that (assuming typical CYA levels, which you have). Some people have trouble with the color-matching thing; I am certainly one of them, although I know many people are okay with it. Finally, I hear that the DPD test can "bleach out" at high FC levels, falsely reading low.

So, that's why we're all pumped about the FAS-DPD test.
--paulr

 

[Butterfly]

Hi mgianzero and welcome to the forum

You've gotten great advice from members here.

You need to shock your pool and you also need an FAS/DPD test kit.

4) I will raise my CYA. The Taylor book says to use a range of 30-50 ppm according to the National Swimming Pool Foundation Handbook of Water Chemistry and also ANSI/APSP. Does this standard change with SWG? Because they make no mention of this in the book..................

You should be following the SWG's manufacturer's recommendations!

Once you are armed w/the info and test kit, we can show you how to keep it cleared and sparkley and algae-free!

and, as PaulR said, we are all pumped up about being able to test up to 50ppm FC

 

[frustratedpoolmom]

See my response to your comments in bold.

Okay, in response to your comments:

1) I have a standard DPD test kit from Taylor. I am not sure the kit #. Where's the number? I have 12 reagents bottles where I can test for chlorine, pH, TA, Calcium hardness, TCA. I really see no reason for a FAS-DPD test kit since this includes most everything I need. I know it measure CC directly, but is it really necessary. My CC was really zero since there was no change in color with R-0003. Isn't this accurate enough?
No, it's not. You have the K-2005, and I highly recommend that you supplement it with the FAS-DPD test I mentioned before, because it's not a comparison test, it's a drop-count test, and it can test FC up to 50 ppm. It's much more simple and accurate to use.

2) These results are mine, but very similar to the pool store's measurements. The only thing I could not measure was salinity except for reading it on my Aquarite system. (It read 2700 and I added a 40# bag which should raise it another 300 ppm to 3000 ppm).
That's fine, it was just for clarification.

3) With all due respect, my chlorine level has always been very high (3+-5+). Before my new kit I could only measure TC. But repeated visits to 2 different pool stores confirmed my FC was b/w 3+ and 5+. It hasn't been read low for quite some time (maybe 8 mos-1 year if even that).
With all due respect, FC of 3-5 is not "very high" at all, and depending on one's CYA level, it's not uncommon to run with a normal level of 8-10 ppm. That still wouldn't prevent an algae outbreak in certain conditions.

I'm sorry, I'm not sure why you are seemingly offended by my attempts to assist you. Pool Stores test results are NOTORIOUSLY inaccurate, and I wanted to clarify whose results you were posting. Since you stated the salt test was theirs, I wanted to be sure. I would trust your kit's results over their's any day. And nothing in my comments were meant to be offensive, so please understand that I am only trying to help.

4) I will raise my CYA. The Taylor book says to use a range of 30-50 ppm according to the National Swimming Pool Foundation Handbook of Water Chemistry and also ANSI/APSP. Does this standard change with SWG? Because they make no mention of this in the book. I will shock with 10 lbs of dichlor since I already have this and I need to raise my CYA anyways. Then I'll remeasure my TCA in a few days.
Yes, if you see the articles on Water Balance for SWG's and Recommended Levels in Pool School, you will note the recommended level for CYA is 70-80 for SWG's and some manufacturers recommend 100ppm. Check your SWG manual for your unit's specific recommendation, if they give one.

I wouldn't do the 10lbs of Dichlor all at once, that would raise your FC too high for your current CYA level - see the CYA chart - the link is in my sig

3) My pH has been a bit high (maybe as high as 7.8 but mostly around 7.6). I usually always have to add muriatic acid to bring it down. Maybe a pint or 2 at a time.
If the recurring addition of adding Acid is bothersome, you can try Lowering your TA to 70 or Adding Borates, if you like, tis entirely up to you. Instructions on how to do both are in Pool School.

4) Regarding my turnover, I run my pool on high speed for 1 hour (enough to skim the surface and the spa spill over). This is around 105-110 GPM according to my flowmeter. (I know it's high flow, but that's because just re-plumbed my system and it flows much better now. Then I run my pool circulation on lo-speed for 7 hours (this measures at 50 GPM). That's more than one turnover per day.

And probably not enough, if that is in fact, algae. If it does prove to be algae, I would recommend either running on low speed 24/7 or increasing the amount of time on high speed to minium of 4 hours. MHO, take it or leave it.

5) This leads me to my real pressing question ... why did I get algae and what type is it? Taylor's manual talks about "breakpoint chlorination" or superchlorination to destroy high levels of combined chlorine, but my CC read zero according to my kit and the pool store.

My personal opinion is if that is algae, its from poor circulation caused by not enough pump run time, and not enough brushing of the pool surfaces.

Also of note:

There are few ways to diagnose algae or organic consumption of chlorine-

Do an "overnight FC test". With the SWG OFF, You test after dark, record the result. Test again in the morning, before the sun hits the pool. If you lose more than 1ppm of FC, you have organics consuming your chlorine (likely algae) and you should shock the pool. Read about How to Shock your pool and Defeating Algae in Pool School.

You can put rub a trichlor tablet on the green stains, and if they fade, they are organic.

Would you have any reason to suspect copper? The use of a mineral ionizer system like Nature 2 or Pool Frog? The use of copper-based algaecides?

There are additional ways to determine if the stains are metal... it is very hard to tell what it is from the pic you posted....

You stated they don't feel slimey, do they brush off?

Does your wall look at all like this:

Hope this helps. Again, that's all we're trying to do.

GMTA - Butterfly - you beat me to it!

 

[JasonLion]

Your picture looks kind of like algae and it also looks kind of like mild metal stains. I can't really tell from the picture which it is.

Neither the Taylor book or the National Swimming Pool Foundation Handbook of Water Chemistry have been updated to fully take into account how SWGs work and what the best water balance for them is. Even though SWGs have been around for over 40 years, they have only really taken off in the last 10 years, and new things are still being discovered about the best way to balance your water with a SWG. The major book authors simply don't update their material that quickly.

One of the things we do here is talk to lots of different people who are trying lots of different ways to take care of their pools and sort out what works and what doesn't work. Using that information we have developed a collection of practices that help SWG owners get consistent and reliable results. When problems come up we update our recommendations quickly, and get the new procedures out to lots of people for testing and feedback.

That doesn't mean that everything we say is perfect, but it does mean that there has been a lot of thought behind the basic approach and there are solid reasons why we recommend most of the things we recommend.

From what you have said, particularly given the flowmeter measurements you quoted, your circulation sounds fine.

I am more concerned about the low CYA level. CYA at 35 will allow the FC level to fluctuate over the course of the day, and it is quite likely that it gets low in the late afternoon. Low CYA levels will also cause the PH to fluctuate more than higher CYA levels do. If that is algae, low CYA levels combined with a SWG is sure to be the ultimate cause.

Your fairly high current FC level and fairly low phosphate level tends to argue against that being algae.

Do you know how quickly the "stain" developed? Did it appear overnight, or spread slowly? Do you use well water or live in an area where iron stains in the sink are common? Did you use a copper based algaecide recently and/or regularly over a period of time?

 

[Guest]

Frm the picture it looks like algae that is probably being caused by dead spots in the pool where the chlorine is depleted by the low CYA levels and poor circulation because of running on low speed for most of your run time. Most SWG manufacturers recommend around 80 ppm CYA and the lowest I have ever seen is 50 ppm but only if the pool does not receive a lot of direct sunlight.

As far as test kits, there is a HUGH difference in the DPD test and the FAS-DPD test in terms of range (it can test up to 50 ppm FC, 10x as high as the DPD test), precision (to .2 ppm) and accuracy (it is a titration test so you are not trying to color match to a comparator). If you already have a K-2005 I would suggest adding the FAS-DPD test to it to give you the same functionality as the K-2006.

As far as the Taylor booklet, don't take it as the gospel truth. It contains quite a bit of misinformation and does NOT take SWGs into account at all.

This thread might be helpful to you:
water-balance-tips-for-a-swg-t3663.html

IT explains that having the proper CYA levels not only will make sure you have enough chlorine but also how it will help with pH control.

You stated you have an Aquarite, what percentage is it set to, and how many hours a day of pump run time do you have? Your salt should be 3200-3400 ideally (not lower than 3200) and your cya should be 70-80 ppm with 80 being better!

 

[mgianzero]

Well, that's a lot of help in such a short period of time! I appreciate all your input.

So, in answer to most all of your questions ...

1) I figured out that the kind of Taylor test kit I bought from Leslie's pool (biggest dealer out here) is Leslie part #81330 with the 12 reagent bottles. I don't know what the actual Taylor # is since I don't see it anywhere on the box or in the instruction book. I also don't see a way to add a FAST-DPD setup to this kit since there is no room for any additional bottles in the box. So how do I do this? Do I REPLACE some of the reagents with a FAST-DPD type or do I need to buy another kit. This kit was $55 and the FAST-DPD is around $65, so I'd hate to waste the money on a new kit and not use it. Ideas?

2) I am really convinced that my problem is algae and not a metal reaction. There would be no reason since I do not use any metal treatment in my pool. I showed it to my neighbor and he tells me that it is definitely algae. He says it looks more like mustard algae, like he had. The algae is not slimy but it brushes very easily from the wall (makes a small dust cloud when I brush it.) He shocked his pool and then used "yellow-out" and it was gone. I think it makes more sense that it's mustard algae since my FC has always been very high (lowest is 4+ and currently it is at 5+) and my understanding is that mustard algae is more resistant to high FC than green algae. It just has a greenish color to it.

3) I am bumping my TCA up to 60-80 ppm since this is recommend for this SWG. I agree that this is a bit low for a saltwater pool.

4) Regarding my possible poor circulation as a cause ... although I am using my 2-speed pump on low speed for 7 hours, it moves 50 GPM according to my flowmeter. Shouldn't this be enough water circulation for a 22,000 gallon pool? I hate to run on high speed very long (at 105 GPM) because it costs so much to run out here in California at 26 cents per kW! The pool was remodeled and it has vibrant spa spillway and 3 return lines which I have directed upwards and creating a somewhat circular motion in the pool to add in skimming. Is this not right? Should I have more return lines?

5) I think once I get this algae out I will try this Borax idea I hear about. Since my pH tends to run high (I'm always adding acid) and algae is tough to get rid of, I think this should help. Agree?

 

[Guest]

Well, that's a lot of help in such a short period of time! I appreciate all your input.

So, in answer to most all of your questions ...

1) I figured out that the kind of Taylor test kit I bought from Leslie's pool (biggest dealer out here) is Leslie part #81330 with the 12 reagent bottles. I don't know what the actual Taylor # is since I don't see it anywhere on the box or in the instruction book. I also don't see a way to add a FAST-DPD setup to this kit since there is no room for any additional bottles in the box. So how do I do this? Do I REPLACE some of the reagents with a FAST-DPD type or do I need to buy another kit. This kit was $55 and the FAST-DPD is around $65, so I'd hate to waste the money on a new kit and not use it. Ideas?
Either order only the FAS-DPD kit from TFTestkits http://www.tftestkits.net/index.php?act=viewCat&catId=6 or from Taylor http://www.taylortechnologies.com/produ ... KitID=2185 . They both use the exact same Taylor reagents. TF testkits is a better deal for the money since it contains 2 oz of titrant instead of .75 oz like the Taylor kit but it does not include a box. Yo can do twice as many tests if you forgo the box!

2) I am really convinced that my problem is algae an
d not a metal reaction. There would be no reason since I do not use any metal treatment in my pool. I showed it to my neighbor and he tells me that it is definitely algae. He says it looks more like mustard algae, like he had. The algae is not slimy but it brushes very easily from the wall (makes a small dust cloud when I brush it.) He shocked his pool and then used "yellow-out" and it was gone. I think it makes more sense that it's mustard algae since my FC has always been very high (lowest is 4+ and currently it is at 5+) and my understanding is that mustard algae is more resistant to high FC than green algae. It just has a greenish color to it.
It does not look like Mustard to me but green algae.

3) I am bumping my TCA up to 60-80 ppm since this is recommend for this SWG. I agree that this is a bit low for a saltwater pool.
And is one of the reasons for both your algae and ph problems. You DID read the link I posted above on water balance tips for SWGs, didn't you?

4) Regarding my possible poor circulation as a cause ... although I am using my 2-speed pump on low speed for 7 hours, it moves 50 GPM according to my flowmeter. Shouldn't this be enough water circulation for a 22,000 gallon pool? I hate to run on high speed very long (at 105 GPM) because it costs so much to run out here in California at 26 cents per kW! The pool was remodeled and it has vibrant spa spillway and 3 return lines which I have directed upwards and creating a somewhat circular motion in the pool to add in skimming. Is this not right? Should I have more return lines?
Doesn't mean that there are not dead spots that ,combined with the low CYA and sunlight exposure had created spots of little or no chlorine and allowed algae to grow. It is one of the drawbacks of two speed and multispeed pumps that are not often publicized that, in your particular case of poor water balance, lead to algae.
5) I think once I get this algae out I will try this Borax idea I hear about. Since my pH tends to run high (I'm always adding acid) and algae is tough to get rid of, I think this should help. Agree?

Getting your CYA in line and dropping your TA to 70 ppm will help also! I would recommend dropping the TA before adding borates.

 

[spishex]

4) Regarding my possible poor circulation as a cause ... although I am using my 2-speed pump on low speed for 7 hours, it moves 50 GPM according to my flowmeter. Shouldn't this be enough water circulation for a 22,000 gallon pool? I hate to run on high speed very long (at 105 GPM) because it costs so much to run out here in California at 26 cents per kW! The pool was remodeled and it has vibrant spa spillway and 3 return lines which I have directed upwards and creating a somewhat circular motion in the pool to add in skimming. Is this not right? Should I have more return lines?

They need to be aimed down toward the floor. You can still angle them left or right which will create enough circular motion up top to keep the surface skimmed, but the pool depends on the returns to properly distribute chlorine and keep water moving across the walls and floor.