Acid turns yellow when added

waste

TFP Expert
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Mar 29, 2007
4,160
Coastalish 'down easter'
Hey all :wave:

One of the pools I now work on is an indoor bromine double treadmill pool (plaster, ~ 10 X 45', 3.5 -> 4.5', 'reverse sport pool', bromine (tablet feeder), 7000 gal. ~ 5 months old)

As said, this pool has 2 high flow 'aqua treadmill' jets, one at either end.

The pH is always on the high side. SI (from Taylor watergram - sorry, no full #s) is .25 @ pH = 7.4 [my bad, I adjusted the pH down to 7.4, from ~8.0] before running the full tests, ~ 6 hours later :oops:

From memory: the TA was 70 and the CH was 230. Temp is maintained @ 81*

Whenever I add acid to this pool to lower the constantly 7.8+ pH - it looks like I added pee to the pool - i.e. a yellow cloud where the acid was poured.

This is a new one for me; is it the bromine, the high pH, or metal (which I doubt)?

This pool will only be running for another week before it's closed and I'd like to address any issue before it gets ignored for 6 months :wink:

Thank you my TFP friends, for any insight you may be able to shed :bowdown:
 

chem geek

TFP Expert
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Mar 28, 2007
12,082
San Rafael, CA USA
When chlorine is added to a bromine pool (a pool with bromide in it) it can produce so much hypobromous acid locally that some have said it looks yellow (or perhaps it initially produces bromine liquid that looks yellow until it combines with water to produce hypobromous acid). I haven't heard this happening when adding acid, but it's possible that the acid creates more dissolved bromine liquid (Br2) from hypobromous acid (HOBr) though that would be red-brown when concentrated, but perhaps looks yellowish when very dilute. Does the color dissipate after mixing?
 

teapot

In The Industry
Jul 25, 2009
574
London and France
As it's an indoor pool, could it be an effect of the lighting until the acid is fully dispersed? As well as the hyperbromous acid Richard posted.
 

Bama Rambler

Mod Squad
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Jun 22, 2009
23,036
SouthWest Alabama
Change brands of acid and see if that makes a difference.

Most HCL is made with DI water that has an added step of R/O filtering right at the makeup point to make sure pipe contamination is taken out of the equation, but some mfg's don't run the makeup water through an R/O filter so a little iron gets left in it.
 

waste

TFP Expert
LifeTime Supporter
Mar 29, 2007
4,160
Coastalish 'down easter'
Thank you for the responses! :cheers:

The guy I work with said that it looks orange/ red when he adds it (I always turn on the 'aquatreadmills' first and dribble the acid into the strong flow) )

I've used 2 different brands of MA with the same result. And, I've added both brands of acid to the other pools with no sign of yellow, though they are all chlorine (puck :rant: :puker: :pukel: )

Richard, I think you may be right on the hypobromous acid - the color quickly dissipates. Are there any tests I can run to confirm this hypothesis? (I'm conversant with the scientific method and will do my best to perform any controlled tests you can come up with to support or refute the theory)

Thank you all for the input! :whoot:

(BTW - the lighting doesn't seem to play any roll - Thanks Teapot :cool: )
 

X-PertPool

TFP Expert
In The Industry
Jun 12, 2009
1,385
Exeter, PA
chem geek said:
When chlorine is added to a bromine pool (a pool with bromide in it) it can produce so much hypobromous acid locally that some have said it looks yellow (or perhaps it initially produces bromine liquid that looks yellow until it combines with water to produce hypobromous acid). I haven't heard this happening when adding acid, but it's possible that the acid creates more dissolved bromine liquid (Br2) from hypobromous acid (HOBr) though that would be red-brown when concentrated, but perhaps looks yellowish when very dilute. Does the color dissipate after mixing?
I was going to mention a similar experience. I had a pool that was using bromine tablets through a feeder and I started adding cal hypo through the skimmer. The return lines would shoot out a green cloud. It wasn't yellow but maybe it looked more green because of the blue liner
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
waste said:
Richard, I think you may be right on the hypobromous acid - the color quickly dissipates. Are there any tests I can run to confirm this hypothesis? (I'm conversant with the scientific method and will do my best to perform any controlled tests you can come up with to support or refute the theory)
If you notice that the intensity of color when adding acid varies with the bromine concentration and that there is little or no color when there is no bromine in the water, then creation of liquid bromine is the likely culprit here. Thanks for confirming the orange/red appearance as that makes it very likely to be creation of liquid bromine in the water. As this gets more diluted and the pH rises towards the pool average, the liquid bromine will react with water to produce hypobromous acid.
 

Pontiac

In The Industry
Aug 30, 2009
30
Northern CA
Hypobromous acid...thanks for explaining Richard.

I have seen this happen in above ground spas, where the elevated bromine levels were giving false high PH readings and acid was mistakenly added. The result was red/orange/brown colored water that did not disapate until soda bicarb was introduced.
 

waste

TFP Expert
LifeTime Supporter
Mar 29, 2007
4,160
Coastalish 'down easter'
To keep this all on the boards:

Richard PM'd me a few tests to do (which will have to wait a few days before I go to work again and can perform them :| )

With the bromine feeder we have (it's a CL 220 for bromine use - i.e. tab fed off line auto brominater) it's proven to be impossible to get the bromine test to show below 10 - you just can't set the dial on the unit low enough to give any less - the pool pump (was) run 24/ 7 per health department 'rules'. [I'm gonna get MY CPO this winter, so I have the 'credentials - I've printed out Richard's "WHAT'S NOT TAUGHT" for myself and the GM]

When I do the test's, I'll post the results here, so as to advance the 'sum of human knowledge' some :mrgreen:
 

dsime42

Member
Sep 29, 2013
15
~Stockton, Ca
Last post on this thread is:
Posted Three years ago and says:
"When I do the test's, I'll post the results here"

Hmmm
Anyone know what the results were???
 

X-PertPool

TFP Expert
In The Industry
Jun 12, 2009
1,385
Exeter, PA
chem geek said:
When chlorine is added to a bromine pool (a pool with bromide in it) it can produce so much hypobromous acid locally that some have said it looks yellow (or perhaps it initially produces bromine liquid that looks yellow until it combines with water to produce hypobromous acid). I haven't heard this happening when adding acid, but it's possible that the acid creates more dissolved bromine liquid (Br2) from hypobromous acid (HOBr) though that would be red-brown when concentrated, but perhaps looks yellowish when very dilute. Does the color dissipate after mixing?

I've seen this in person with bromine. We took over a pool for weekly maintenance, it had a bromine feeder and we switched to using cal-hypo. Whenever you added a large dosage of cal-hypo to the skimmer it would eventually shoot out a green cloud from the returns (yellow + blueish water and liner). It took about an entire season to finally stop.
 

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