FC problem - not sure if related to biofilm or not

[vdo]

I have a new spa that I installed and filled. Got the recommended test kits and check things every day and when things first started out, I was going along fine. I am following Nitro's post and adding dichlor until I get the right CYA value and then use bleach. I use boric acid (my wife really likes the feel of the water with it) and use dry acid to bring down pH and it all works as expected.

I test every day, sometimes more than once a day to try and make sure my FC levels do not go to 0.

But even with that, after a few days, my FC started to go to 0 overnight (even when starting from a level 10). I found a thread that said new tubs can have biofilm after having water sit in them from the factory water tests. So I used Ahhhsome Spa purge/cleaner (actually ran it through, drained it, filled it ran another batch, and then drained and filled it again twice to make sure). I had FC up to 20 just to make sure it would kill what got broken up.

Thought I was in the clear as I started new and had about a week of things going fine, but FC started going to 0 fast again and today water looks pretty cloudy. I am thinking this must be that the biofilm did not get killed completely and the only thing I can think of doing is another purge with maybe a higher FC shock. I just can't see otherwise how things can go south so fast without it being a biofilm that is responsible.

Is there anything else I should do? Is there an upper limit too how much bleach I should add as I don't want to damage any equipment.

 

[vdo]

So I added enough bleach that the Pool Math Calculator said would raise FC to 8, but after I waited several minutes and tested, it showed no FC. I waited an hour then added the same amount of bleach again and waited 20 minutes and still no FC. I then decided to add Dichlor (enough for 8 FC even though I had already added enough to get me to to 30 CYA in the beginning of the week and did not think it would have dropped at all). After that my K-1000 kit showed at the max level. Not sure if it was coincidence that I used dichlor or if bleach would have registered at that point also if I had done one more round of it instead. Also I am not sure why FC did not register at first and then finally did. Not sure if the biofilm I am suspecting was using it up instantly and I needed to cross a threshold. Again, I am going to purge this water, but I was trying to get FC to a shock level before I did that and did not expect it to take so much bleach/dichlor to get there.

 

[jseyfert3]

Is your bleach bad? How old is it? There should be a 5 digit data code in the form of YYDDD printed on the bottle somewhere. For example, 17339 means it was manufactured the 339th day of 2017.

Based on what you've said, it sounds like the FC is fine originally, when you are using dichlor on a new fill, but you have issues when you start using bleach. Is this correct? Do the issues only start when you start using bleach, but everything is fine on an initial fill with dichlor? If so, that also points to bad bleach.

 

[vdo]

Is your bleach bad? How old is it? There should be a 5 digit data code in the form of YYDDD printed on the bottle somewhere. For example, 17339 means it was manufactured the 339th day of 2017.

Based on what you've said, it sounds like the FC is fine originally, when you are using dichlor on a new fill, but you have issues when you start using bleach. Is this correct? Do the issues only start when you start using bleach, but everything is fine on an initial fill with dichlor? If so, that also points to bad bleach.

Wow, thanks, that must be the problem - I did not realize bleach went bad and I'm so glad I posted here as I would have kept going bonkers trying to figure this out!

Yes, you are correct that the FC was fine originally when using dichlor and then the issues started when switching to bleach.

My bottle had two lines, one starting with the letter A followed by 7 digits and then another line with 4 digits with a dash and letter/number combo.

I think bleach brands must vary on how they do their date codes as I checked on the Clorox site and they said: "The top line has a letter followed by a 7 digit code. The letter and first number are producing plant identification; the next 4 digits are a Julian production code and the final 2 digits are a shift identification. The second line is the EPA registration number (5813) followed by a state identification code"
(here is the link)

Sure enough, mine was a few years old.

Thanks so much again for replying and clearing this up for me!

 

[jseyfert3]

No problem. Just passing along info I've received myself!

From what I've read here bleach can get to half strength or so within 6 months of manufacturing. Depends on storage conditions. Several years is probably just salty water.

ANOTHER CAUTION as you get new bleach. Apparently all Clorox bleach now is splashless, which you do not want. Will cause lots of foaming. Most people get generic Walmart Great Value brand. Anything that doesn't have fragrances or isn't splashless should be good.

 

[vdo]

Yeah, I ended up getting another brand (Simply Done) because it was clear on the concentration (8.25% and so better value than similarly sized other ones that were 6%) where I wasn't finding that clearly on the Chlorox bottles. I'll have to check out the Walmart ones for cost/value.

There were a lot of splashless Chlorox ones like you say but they still had stock on non-splashless Chlorox ones (so they are probably aging)

The non-splashless ones all mentioned Chloromax stain repelling and I thought any kind of additive is not good. Sure enough I found a thread on this forum that says Chlorox says the additives are a polymer and not meant for pools and so it looks like Chlorox is not a good choice even if they had kept the non-splashless version.

 

[Arobbert]

You can also go to a pool store and buy liquid chlorine shock. I picked up a case for $15. A lot of big box stores like Home Depot or Lowes will carry this as well. The concentration is usually around 12.5%.