OTO Test started at 4, then turned dark orange. High CCs?

[AndyPoolSpa]

I've looked around this forum for a while, but this is my first post.

The pool runs on bromine.
The sun breaks down the bromine rapidly, so this morning I put 2 trichlor tablets in the chlorinator to try to use less chlorine bleach. My understanding is the chlorine activates the bromide.

This evening I tested the chlorine/bromine level with the OTO test that comes in the TF-100. The pH was normal, 7.5. The chlorine level was about 4, but in the next several minutes it got darker and darker. Now it's a dark orange color.
I did a little research and it seems the color change is due to CCs. That would suggest I have over 10 ppm of CCs!

Just yesterday morning I tested the pool with the FAS-DPD. I had tested it the previous evening as 11 ppm, and in the morning it was 10.5 ppm, so I would say it passed the OFCLT.
But most importantly, both FAS-DPD tests showed only about 1 ppm of CCs.

How could the CCs jump up so quickly?!
Any suggestions on how to handle it?
Thanks

 

[Richard320]

Have you used any Potassium Monopersulfate aka "non chlorine shock"? That'll mess up the CC test.

 

[AndyPoolSpa]

I used it in the spa recently, but not the pool. It's possible some MPS was added to the pool years ago.
So, basically no.

Thanks for the quick reply!

 

[JamesW]

How many pounds of bromine tabs have been used since the pool was last filled?

 

[AndyPoolSpa]

Actually, no bromine tablets were used. My bromide came from "Yellow Treat" or "Stop Yellow" that really is just sodium bromide.
As for how many since filling, I don't really know. It's been something like 8 years since filling, so probably something like 20 lbs of it total.

That was before I knew that bromide takes forever to leave the pool. Now I think I might want to switch back to chlorine, but I read that requires a complete drain and refill.

 

[JamesW]

Bromine is not supposed to have a reaction to a combined test.

However, it almost always does.

In some cases, it might be high levels of DMH from the tabs.

I suspect that you might have bromates building up.

How much sodium bromide has been added in total since the pool was last filled?

The balls are made of high density polyethylene (HDPE) which is less dense than water so they float on the surface of the reservoir even if they break apart. They are 10cm (4 inches) in diameter and contain about 210ml of water. So the main reason they are on the reservoir is to block sunlight from entering the water and triggering a chemical reaction that turns harmless bromide into carcinogenic bromate.

 

[AndyPoolSpa]

I answered in my last post.

I haven't used bromine tablets, just chlorine ones, so I don't think there would be any DMH.

Probably something like 20 lbs of sodium bromide over about 8 years.

About the bromates: I thought the chlorine would convert them back to active bromine, but I could be wrong.

It was weird to see the OTO solution turning darker and darker. Do you think I should use the FAS-DPD test or even (I probably shouldn't say this) test strips instead?

 

[JamesW]

Bromates are different than bromide.

Bromine is a weaker oxidizer than chlorine. So, maybe it's reacting slower to the OTO than chlorine would.

How many pounds of chlorine tabs have been used since the pool was last filled?

What is the CYA level?

 

[AndyPoolSpa]

Ok. So bromates can build up. How are they removed? Only by draining and refilling?

I have no idea how many chlorine tablets have been used. I've been back and forth about using them because they raise CYA. I haven't used them recently, until today.

The pool has been partially drained and refilled in the past, sometimes specifically to decrease CYA. The current CYA level is 55.

Interesting video btw. Maybe I should buy some of those! Lol

 

[JamesW]

The bromine really complicates things. Try a FAS-DPD test for FC and CC to see what that shows.

 

[AndyPoolSpa]

Yep, the bromine definitely complicates it!

I did the FAS-DPD test.

Results:
FC: 1.5 ppm
CC: 0.5 ppm

That's weird! It seems like the OTO measures something else. Whatever it was, it either disappeared overnight, or is not tested by FAS-DPD.

Also, I smelled the "fishy smell" in the pool water that is generally associated with bromine. It wasn't very strong, but could that be bromates or is it something else?

 

[JamesW]

Hard to tell what's going on.

Try checking both ways for a couple of days to see if they match.

 

[AndyPoolSpa]

Today's test results, all taken within 30 minutes of each other.

First, the OTO/pH test:
Chlorine level looked like 4, but then, like before, it kept getting darker until it stopped at dark orange.
ph: 7.6

Because it seemed high, I turned off the chlorinator.
Then, I tried a test strip.
TC: 0
FC: 0
ph: 7.5
I used to have confidence in the strips, but now I doubt their accuracy. But who knows, my pool water is definitely weird.

So then I tried the FAS-DPD.
FC: 1
CC: 1

After this, I swam in it, then turned the chlorinator back on. Am planning to add some chlorine/bleach later today.
Very strange how different the results are. I can't tell if the pool has a problem or not.

 

[AndyPoolSpa]

I don't know if this is at all related or not, but there are some stains in the pool.

Several of them are rust colored and have been there for many years. I think they are iron. I haven't tried Ascorbic Acid on them yet.

More recently, I noticed grey colored stains. I thought they were black algae at first, but brushing and a SLAM didn't remove them. Could these be copper stains? Copper could have come from Clorox "Xtra Blue" granular trichlor that I used in the past.

With all that said, maybe I should should start a new thread specifically about the metal?
I don't know if I'm ready to try to remove the metals. From what I've read it is a long and expensive process.