Algae forms because pool won't maintain FC level even after slam

[Ecrivan]

I can't figure out what's going on with my pool. I switched to the BBB method 2 summers ago and generally, it has worked for me. But I find I'm spending a lot on bleach because my pool water drops to around 0 FC after a bleach slam the day before. And of course, because it won't hold an FC level, I start to get algae.

The readings on my 20,000 gal plaster pool are as follows:
PH = 7.4
TA = 110
CH = 500
CYA = 50-55
Borates = 60

I run the pump 6-8 hours/day.

I have enough CYA that my pool should be holding a steady FC level. But after shocking it (putting in enough bleach to bring it up to ~16ppm FC), it is down to 0 again in less than a day. What gives?

I have already followed the directions in the article about turning your green swamp into a sparkling oasis, and the overnight test showed I had eliminated all of the algae. But now it's creeping back again because the pool won't hold the bleach. Should it be growing back that fast (less than a week)?

Please help.

 

[chem geek]

So to be clear, the chlorine is holding overnight with <= 1 ppm FC loss but you lose it all during the day? If so, are you sure the CYA level is as high as you say?

I also assume you have a FAS-DPD chlorine test, correct? Either the TFTestkits TF-100 or Taylor K-2006 test kits, right?

Maybe during one time when the chlorine went to zero your CYA got consumed by bacteria. Is the CYA reading you listed a recent reading?

 

[PAGirl]

Are you only going to shock level once in the day for day, or are you keepin it at the shock level (now called SLAM) until you dont have a loss of moee than 1 over night? They have changed the guidelines for the SLAM slightly, you may want to reread.

 

[Ecrivan]

No, the chlorine is not holding overnight. I am slamming it probably 3x a day, but the next day, it's down to zero. I can't babysit the pool and check it every hour (I have a job), so I can only work on it when I get home. The amount of bleach I'm having to buy is making the BBB method cost-prohibitive. So much for having a "Trouble Free Pool".

I do have the Taylor FAS-DPD kit and I get a CYA reading of between 50-60 consistently. And I'm told that my phosphates (2500) and CH (500-610) are so high that I won't be able to affect my pool with any amount of bleach/chlorine. I just dumped and refilled the pool 2 years ago. Do I already have to do it again? And if so, how has the BBB method helped me? What makes the CH rise so high so fast?

Please help. I'm at the point where I'm considering filling in the pool and reclaiming my yard.

 

[Donldson]

The problem is you did not SLAM it. Something is growing so I suggest you reread the SLAM article. Phosphates never factor in to chlorine consumption, if you are going to try to mix TFP advice and normal pool store advice then you are going to fail. Finally, we all have jobs, kids, other obligations, etc. I apologize if that seems blunt, but the system works. It's up to you to work the system however you are able to.

 

[bridgman]

And of course, because it won't hold an FC level, I start to get algae.

It's the other way round. Because you have algae, it won't hold an FC level. A "proper" SLAM should get bleach consumption back down.

Most folks end up starting the SLAM on the weekend (or whatever days they aren't working) and it usually gets to the point where 2-3 checks a day are enough before the end of the weekend.

 

[scott.MI]

Responses in red

I can't figure out what's going on with my pool. I switched to the BBB method 2 summers ago and generally, it has worked for me. But I find I'm spending a lot on bleach because my pool water drops to around 0 FC after a bleach slam the day before. And of course, because it won't hold an FC level, I start to get algae.

The readings on my 20,000 gal plaster pool are as follows:
PH = 7.4
TA = 110
CH = 500
CYA = 50-55
Borates = 60

I run the pump 6-8 hours/day.

I have enough CYA that my pool should be holding a steady FC level. But after shocking it (putting in enough bleach to bring it up to ~16ppm FC), it is down to 0 again in less than a day. What gives? With CYA at 50, slam is 20, and CYA of 55 is 22. I would treat it as 60 and SLAM to 24 every chance you get. Alternatively you could do a partial drain and slam with a lower CYA

I have already followed the directions in the article about turning your green swamp into a sparkling oasis, and the overnight test showed I had eliminated all of the algaeIf your losing chlorine over night, you didn't eliminate it all. Chlorine is consumed by sunlight and organics like alage. If you lost it all over night that sums up your situation. But now it's creeping back again because the pool won't hold the bleach. Should it be growing back that fast (less than a week)?

Please help.

 

[scott.MI]

My comments in red

No, the chlorine is not holding overnight. I am slamming it probably 3x a day, but the next day, it's down to zero.Covered previously, only sunlight and organics like algae consume chlorine. I can't babysit the pool and check it every hour (I have a job), so I can only work on it when I get home. The amount of bleach I'm having to buy is making the BBB method cost-prohibitive. So much for having a "Trouble Free Pool". Something happened where your chlorine levels got too low and allowed algae to get established.

I do have the Taylor FAS-DPD kit and I get a CYA reading of between 50-60 consistently. And I'm told that my phosphates (2500) and CH (500-610) are so high that I won't be able to affect my pool with any amount of bleach/chlorine. I just dumped and refilled the pool 2 years ago. Do I already have to do it again?There is not anything here that can't be fixed with a proper session of SLAMing to 24PPM and and some daily maintenance after. And if so, how has the BBB method helped me? What makes the CH rise so high so fast?Depends on what the CH in your fill water is and how much water and how often you add.....but when your water evaporates, all the calcium stays behind so when you put more water in, you now just got a raise in your CH.

Please help. I'm at the point where I'm considering filling in the pool and reclaiming my yard.

Summary notes....You still have algae, your proper slam level is 24 not 16. GET'ER DONE.

 

[Ecrivan]

I guess my slamming levels have never been accurate. I was using the Pool Calculator, which usually gave me a slamming level of between 16 and 20. I'll go higher and see what happens. For now, I won't worry about the phosphates.

But I'm still concerned about the CH. No one--here, in the pool store, or anywhere I can find on the internet--can give me a clear reason why it is so high and so soon after a refill. I can't spend the money to drain and refill the pool every 2-3 years, and I'm concerned that these levels (500-610) will prove harmful to my equipment and surface, and prevent the chemicals from doing their job.

Thanks for the help.

 

[Charlie_R]

High CH will NOT affect chlorine usage. There are several members here (desert southwest) that have dealt with CH higher than yours, and have kept a sparkling pool for years. what it will affect is how high or low you can maintain your pH and TA an avoid scaling.

Have you ever used cal-hypo as an chlorinating agent?

When was the last time you checked your fill water? My fill water changes according to the local water table, and how much the water company is willing to spend in removal of the CH in their well water. That is why I check mine at the start of the season at opening, and at least once during. I want to know what's going into my pool.

 

[Richard320]

Test your fill water. If it's high in CH, that's where it comes from. Water evaporates, CH doesn't. It just grows and grows. And if you've ever let the pool store talk you into using Cal-hypo "shock" that's another source. The Calcium doesn't interfere with anything else. It doesn't make CYA or FC less effective or anything. My pool tested at 850 CH this morning (That's down from a few weeks ago thanks to some draining!) and it's crystal clear and there are no patches of grow-your-own sandpaper Calcium Scale anywhere.

Bottom line: no one is going to care if your Calcium is high or low if your pool is a green sludge pit. Deal with your chlorine consumption by doing the

 

[scott.MI]

But I'm still concerned about the CH. No one--here, in the pool store, or anywhere I can find on the internet--can give me a clear reason why it is so high and so soon after a refill. I can't spend the money to drain and refill the pool every 2-3 years, and I'm concerned that these levels (500-610) will prove harmful to my equipment and surface, and prevent the chemicals from doing their job.

Thanks for the help.

If you would consider it, take the time to add your pool info into your signature, and update your profile with a location....sometimes it can help. An idea of your fill water CH level will prove useful also. Something to think about is rain has 0 Calcium and at least 1 member here has diverted his roof gutters to his pool to help manage his rising CH levels.

- - - Updated - - -

I was using the Pool Calculator,

The go to is now "pool math" located at the top of the page...switch out your bookmarks

 

[bobodaclown]

What type of chlorine are you using?
You add chlorine until you kill the nasties (maintain shock level) until you don't need to. You understand that every pool has a daily chlorine demand that must be met.