CYA, mustard algae, chlorine level and out of town

DGroesch

Member
Jun 14, 2021
7
Ottawa, IL
Hello all,
We’re off to a rocky start with our first full season as pool owners. We somehow acquired mustard algae last year, and kind of just kept shocking the pool to keep it at bay. Opened up this year to a swamp, got it clear, and the mustard algae is back. We had no CYA opening, so we put some stabilizer in and got it to a good level. We bought a large box of powdered shock (before actually reading through these threads) from Sam’s and continued to shock when needed. We had a little bit of green water before leaving for a few days, so decided to double up on the powdered shock before leaving in hopes of keeping things at bay. We filled our floating duck with pucks and threw him in. You can probably see where I’m going with this. I’m kicking myself for not reading though here before. Our CYA is currently at 120. We’ve brought it down from 180 by draining to below the skimmer and refilling a couple of times. We know how to bring it down now and that it will just take some time. In the meantime, can we swim? When looking at the CYA/FC chart, we’d have to have our FC somewhere between 8-13ppm. Our test kit only goes up to 10ppm, how do I know what it is if it’s over 10ppm?
Also, we are going out of town again, for 4 days. I don’t want to leave pucks in there (I don’t ever want to use them again for that matter) so what is your best suggestion to keep everything at bay until we return and I can continue lowering the CYA to get to a level where I can slam the pool and then do a mustard algae slam. We have liquid chlorine on hand, and will be getting more for our slam process. Thank you in advance from a frustrated newbie pool owner who just wants to have pretty water 🥲
 

Bperry

Gold Supporter
Aug 20, 2020
2,053
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
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CircuPool RJ-60
Hello all,
We’re off to a rocky start with our first full season as pool owners. We somehow acquired mustard algae last year, and kind of just kept shocking the pool to keep it at bay. Opened up this year to a swamp, got it clear, and the mustard algae is back. We had no CYA opening, so we put some stabilizer in and got it to a good level. We bought a large box of powdered shock (before actually reading through these threads) from Sam’s and continued to shock when needed. We had a little bit of green water before leaving for a few days, so decided to double up on the powdered shock before leaving in hopes of keeping things at bay. We filled our floating duck with pucks and threw him in. You can probably see where I’m going with this. I’m kicking myself for not reading though here before. Our CYA is currently at 120. We’ve brought it down from 180 by draining to below the skimmer and refilling a couple of times. We know how to bring it down now and that it will just take some time. In the meantime, can we swim? When looking at the CYA/FC chart, we’d have to have our FC somewhere between 8-13ppm. Our test kit only goes up to 10ppm, how do I know what it is if it’s over 10ppm?
Also, we are going out of town again, for 4 days. I don’t want to leave pucks in there (I don’t ever want to use them again for that matter) so what is your best suggestion to keep everything at bay until we return and I can continue lowering the CYA to get to a level where I can slam the pool and then do a mustard algae slam. We have liquid chlorine on hand, and will be getting more for our slam process. Thank you in advance from a frustrated newbie pool owner who just wants to have pretty water 🥲
The algae is from too little chlorine and too high CYA.

If you have to leave for 4 days, it’ll be hard. You would be wise to order a Taylor K2006C test kit from Amazon or order a TF-100 from tftestkits. Those have the ability to test FC over 10ppm.

If you fill out your signature with your pool size, someone can calculate how much chlorine to add to bring it up to SLAM level while you go out of town. Maybe even load up the floater while your gone to keep it from getting worse. If the CYA is really 120 you’ll need to drain a lot anyway.
 

Edge70

Well-known member
May 16, 2021
105
Belleville Ontario Canada
Pool Size
22700
Surface
Vinyl
Chlorine
Liquid Chlorine
Sounds like you've been doing some reading so I'm sure you're not going to be surprised to hear the suggestion to get your CYA into a proper range where you can effectively take care of your pool. At 120, it's double where you should have it. Therefore, you're into exchanging 50% of the water in your pool to get it to close to where you want it. As for what to do when you are away, if it were me, I'd have someone come over and add liquid chlorine to it each day. Short of that, I'd stick with the floater so that it doesn't get even more algae and become harder to clean up. Easier to purge some water to lower CYA than to have to battle algae when you return.
 
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DGroesch

Member
Jun 14, 2021
7
Ottawa, IL
The algae is from too little chlorine and too high CYA.

If you have to leave for 4 days, it’ll be hard. You would be wise to order a Taylor K2006C test kit from Amazon or order a TF-100 from tftestkits. Those have the ability to test FC over 10ppm.

If you fill out your signature with your pool size, someone can calculate how much chlorine to add to bring it up to SLAM level while you go out of town. Maybe even load up the floater while your gone to keep it from getting worse. If the CYA is really 120 you’ll need to drain a lot anyway.
I’m sorry, I thought I did fill out my signature, I’ll have to go back to try it again. We have a 27ft round by 52 inch high pool. If I’m correct it’s 17,500 gallons. I was just looking at the tests, I’ll get one ordered. Thank you!
 

DGroesch

Member
Jun 14, 2021
7
Ottawa, IL
Sounds like you've been doing some reading so I'm sure you're not going to be surprised to hear the suggestion to get your CYA into a proper range where you can effectively take care of your pool. At 120, it's double where you should have it. Therefore, you're into exchanging 50% of the water in your pool to get it to close to where you want it. As for what to do when you are away, if it were me, I'd have someone come over and add liquid chlorine to it each day. Short of that, I'd stick with the floater so that it doesn't get even more algae and become harder to clean up. Easier to purge some water to lower CYA than to have to battle algae when you return.
I’ve been reading so much my eyes are crossing. 🤪. We do plan on draining and refilling until we get to the proper CYA level, we just aren’t able to until we get back. I do have someone coming to watch my dogs, so I will ask them to put some chlorine in while they are here also. Good idea. Thank you!
 

Bperry

Gold Supporter
Aug 20, 2020
2,053
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
I’ve been reading so much my eyes are crossing. 🤪. We do plan on draining and refilling until we get to the proper CYA level, we just aren’t able to until we get back. I do have someone coming to watch my dogs, so I will ask them to put some chlorine in while they are here also. Good idea. Thank you!
Have them add one gallon per day.
 
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Jsf721

Well-known member
Jun 24, 2022
134
Long Island, NY
I am a serious newbie but I had this nightmare last year. Mine also came back and only after I cleaned the DE grids 3 days in a row after the pool cleared did I said good bye to it !

During this event I learned my phosphates were high- I used several Phosphate removers and the Orenda PR10,000 was the best in my humble opinion. I also learned that the pucks I used increased my CYA to close to 100 ppm that made my chlorine less effective. Now I watch both of those along with my chemistry more closely and knock on wood I am doing OK.

I have a 34,500 gallon pool. I hit the pool with 10 gallons of super shock liquid, left the filter running 24 hrs a day for a week and only stopped it to clean the filter grids daily. I also brushed the pool a ton Am and PM daily. Once it cleared, I got my chemistry back in order. Super Shocking the pool lead to a no swim pool for 5 days as my FC was off the charts like 11. You could smell the chlorine from 10 feet away. I most likely over did the shock but I mentally needed to defeat the mustard algae so I kind of nuked it.
 

jeffchap

Bronze Supporter
TFP Guide
Jun 26, 2012
2,385
Edmond OK
Pool Size
27500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If your CYA is still 120, you can safely swim with FC anywhere from 8 to 48, pH is between 7.2-7.8 and you can see all the way to the bottom at the deepest point.
 
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DGroesch

Member
Jun 14, 2021
7
Ottawa, IL
I am a serious newbie but I had this nightmare last year. Mine also came back and only after I cleaned the DE grids 3 days in a row after the pool cleared did I said good bye to it !

During this event I learned my phosphates were high- I used several Phosphate removers and the Orenda PR10,000 was the best in my humble opinion. I also learned that the pucks I used increased my CYA to close to 100 ppm that made my chlorine less effective. Now I watch both of those along with my chemistry more closely and knock on wood I am doing OK.

I have a 34,500 gallon pool. I hit the pool with 10 gallons of super shock liquid, left the filter running 24 hrs a day for a week and only stopped it to clean the filter grids daily. I also brushed the pool a ton Am and PM daily. Once it cleared, I got my chemistry back in order. Super Shocking the pool lead to a no swim pool for 5 days as my FC was off the charts like 11. You could smell the chlorine from 10 feet away. I most likely over did the shock but I mentally needed to defeat the mustard algae so I kind of nuked it.
I feel the same as needing to set fire to it and scream just for my mental stability while dealing with it. I’m totally fine with not swimming as long as we can get rid of it and enjoy it for the rest of the summer. Thanks for your input!
 

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Bperry

Gold Supporter
Aug 20, 2020
2,053
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
I am a serious newbie but I had this nightmare last year. Mine also came back and only after I cleaned the DE grids 3 days in a row after the pool cleared did I said good bye to it !

During this event I learned my phosphates were high- I used several Phosphate removers and the Orenda PR10,000 was the best in my humble opinion. I also learned that the pucks I used increased my CYA to close to 100 ppm that made my chlorine less effective. Now I watch both of those along with my chemistry more closely and knock on wood I am doing OK.

I have a 34,500 gallon pool. I hit the pool with 10 gallons of super shock liquid, left the filter running 24 hrs a day for a week and only stopped it to clean the filter grids daily. I also brushed the pool a ton Am and PM daily. Once it cleared, I got my chemistry back in order. Super Shocking the pool lead to a no swim pool for 5 days as my FC was off the charts like 11. You could smell the chlorine from 10 feet away. I most likely over did the shock but I mentally needed to defeat the mustard algae so I kind of nuked it.
You had algae because your chlorine was way too low. If your CYA was really that high, it needs to be “like 11” all the time and it fine for swimming. There’s no reason not to swim in that case.
 

Bperry

Gold Supporter
Aug 20, 2020
2,053
Knoxville, TN
Pool Size
27000
Surface
Plaster
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I feel the same as needing to set fire to it and scream just for my mental stability while dealing with it. I’m totally fine with not swimming as long as we can get rid of it and enjoy it for the rest of the summer. Thanks for your input!
Just follow the SLAM process and you can swim any time. No fire necessary. 😁
 

Bperry

Gold Supporter
Aug 20, 2020
2,053
Knoxville, TN
Pool Size
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CircuPool RJ-60
Is mustard algae really that common? Seems like it’s coming up a lot, myself included. I wish there was a way to positively ID the type.
It’s not, I think people just think it’s mustard algae because it keeps coming back because they keep the chlorine too low.
 

DGroesch

Member
Jun 14, 2021
7
Ottawa, IL
It’s not, I think people just think it’s mustard algae because it keeps coming back because they keep the chlorine too low.
I think that’s exactly what’s been happening to us. When we opened the pool we scrubbed everything washed all the tools and toys, etc. But didn’t realize the CYA had dropped so much over the winter. For whatever reason I thought it was a one and done type of deal. I know now it’s not, thanks to everyone here. I also didn’t fully understand the relationship between CYA and chlorine, so just followed along with the label on the chlorine and kept it between 3-5ppm. I’m hoping to get some good, quality time in the pool and wanting to get the process going! Thanks for all of your help!
 

DGroesch

Member
Jun 14, 2021
7
Ottawa, IL
Just in case anyone else is in the same type of situation, I wanted to update. We left our pool with a CYA of 120ppm, and I dumped 4 gallons of chlorine in it. I had our dog sitter add a gallon each day while we were gone for 3 days. When we came home, I checked the CYA again, just to be sure I was not wrong the last time. Still in the 120-130ppm range. We have friends coming over in a few days, and I’d like to be able to swim, so I decided to dump 13 gallons of chlorine in the pool, in hopes that it would be enough with the high CYA. Turns out, that was a giant waste of money, because 10 minutes after I did, there was 0ppm of chlorine in our pool. At that point, I set up our vacuum hose as a siphon and started draining the pool. I let it drain to below the skimmer and put the garden hose into the pool to add fresh water. I let those both go for a couple of hours, and then took the garden hose out and let it drain some more until it went under the return. We filled the pool back up, and let the pump run all night. When I checked the CYA level this morning, it is in the 60-70 range, so not perfect, but a far cry from the 180ppm we started out with. We will most likely try and manage it with the higher CYA for the rest of this swim season. What a hard lesson learned about powdered shock 🤦🏻‍♀️ Thank you for all of your help!
 

Bperry

Gold Supporter
Aug 20, 2020
2,053
Knoxville, TN
Pool Size
27000
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Plaster
Chlorine
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CircuPool RJ-60
Just in case anyone else is in the same type of situation, I wanted to update. We left our pool with a CYA of 120ppm, and I dumped 4 gallons of chlorine in it. I had our dog sitter add a gallon each day while we were gone for 3 days. When we came home, I checked the CYA again, just to be sure I was not wrong the last time. Still in the 120-130ppm range. We have friends coming over in a few days, and I’d like to be able to swim, so I decided to dump 13 gallons of chlorine in the pool, in hopes that it would be enough with the high CYA. Turns out, that was a giant waste of money, because 10 minutes after I did, there was 0ppm of chlorine in our pool. At that point, I set up our vacuum hose as a siphon and started draining the pool. I let it drain to below the skimmer and put the garden hose into the pool to add fresh water. I let those both go for a couple of hours, and then took the garden hose out and let it drain some more until it went under the return. We filled the pool back up, and let the pump run all night. When I checked the CYA level this morning, it is in the 60-70 range, so not perfect, but a far cry from the 180ppm we started out with. We will most likely try and manage it with the higher CYA for the rest of this swim season. What a hard lesson learned about powdered shock 🤦🏻‍♀️ Thank you for all of your help!
If you lost that much chlorine in 10 minutes, it’d be wise to do an ammonia test.
 
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Newdude

Mod Squad
Gold Supporter
TFP Guide
Jun 16, 2019
17,259
NY
so I decided to dump 13 gallons of chlorine in the pool, in hopes that it would be enough with the high CYA. Turns out, that was a giant waste of money, because 10 minutes after I did, there was 0ppm
We're you using test strips ? 13 gallons of 10% is 75 FC. You bleached the test strips color pad off with 75 FC.
If you lost that much chlorine in 10 minutes, it’d be wise to do an ammonia test.
They still had CYA. Ammonia eats both. Something isn't adding up here.

@DGroesch you almost certainly still need to SLAM Process. You exchanged some water but still have old water festering.
 

jeffchap

Bronze Supporter
TFP Guide
Jun 26, 2012
2,385
Edmond OK
Pool Size
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Sorry, but you're having trouble because you're not really following the TFP method. There is a science behind what we do. Nothing here would ever advise you to blindly dump 13 gallons of chlorine in your pool. We never add anything to our pools without a specific reason and in specified amounts.

I agree with Newdude that your FC level, rather than being zero, was probably so high that it bleached out your test strips -- another reason we don't use them.

Until you get one of the recommended test kits and start adding chemicals based upon those verifiable results, you're just setting yourself up for more frustration.

Test Kits Compared
 
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Bperry

Gold Supporter
Aug 20, 2020
2,053
Knoxville, TN
Pool Size
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Plaster
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CircuPool RJ-60
We're you using test strips ? 13 gallons of 10% is 75 FC. You bleached the test strips color pad off with 75 FC.

They still had CYA. Ammonia eats both. Something isn't adding up here.

@DGroesch you almost certainly still need to SLAM Process. You exchanged some water but still have old water festering.
Ah, I assumed a Taylor kit was being used. Yea, if strips were the measurement method then bleaching out is a more likely explanation.
 

Mdragger88

Bronze Supporter
TFP Guide
Jun 1, 2018
6,499
Hernando, Ms
Pool Size
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Dump & pray is not the method here. You have certainly risked your liner & equipment along with needlessly wasting alot of liquid chlorine.
Don’t add anything else until u can test properly.
If u think your fc level is anywhere above slam level for your cya- that is definitely not safe for swimmers.
Did u get a test kit?
Taylor k2006c
Or tf100 are the only ones recommended here- they contain all the tests u need to follow the SLAM Process & safely eradicate algae.
That much chlorine very likely bleached a test strip.
 

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