Drain and Refill - Water turned yellow - Can't figure out why?

MPurcell

Well-known member
Feb 17, 2017
105
Dahlonega, Georgia
I switched from bromine to chlorine, using the dichlor then bleach method, three months ago. Everything went normally on the switch over during both setup and use for three months. Because of a gradual buildup of combined chlorine, I decided to go ahead and do a drain and refill now.


So yesterday I drained and cleaned and refilled. I did not use Ah-some this time since I did an Ah-some purge three months ago, and the tub was new six months before that. I then balanced the water chemistry as follows:


Tub is 330 gallons when full. Fill water is well water. pH ~6.5, TA 20, CH 25. Fill temp is 66 deg F.


Added 9.0 oz of 99.9+% pure boric acid from Florida Laboratories to bring borates up to calculated 50ppm.


Added 4.4 oz of calcium chloride to bring CH up to calculated 150ppm.


Added 3.25 oz of baking soda to bring TA up to calculated 80ppm.
Checked pH with test kit. Reading at 7.4.


Added 2.45 oz dichlor to bring CYA up to calculated 40ppm. This also brought chlorine up to calculated 44ppm.


Added 1.5 oz of 35% hydrogen peroxide to neutralize most of the chlorine. Calculation called for 1.75 oz but the 1.5 oz actually neutralized the chlorine down to zero.


Added 1.5 oz of bleach to bring the Chlorine up to calculated 4ppm.
Checked FC 3.5 ppm, CC 0.


At this point, water is beautifully crystal clear and I put the lid on and set the heater to bring it up to about 90 deg F overnight. Chemistry should be, by calculation:
FC 3.5 (tested)
CC 0
pH 7.4 (tested)
TA 80
CH 150
CYA 40
Borates 50


This afternoon, I lifted the lid breifly to take a water sample to test the chemistry and adjust parameters if necessary. Following results:
FC 3.0
CC 0
pH 7.2
TA 70
CH 150
CYA 30 (not sunny today so not sure)


I decided to add a little more baking soda to bump the TA and pH up, so I took the lid off, and was greeted with very yellow water. I'd say the color is more yellow brown than green anyway. My wife described the color as brownish green. The wall next to the tub is dark blue so the light reflecting from it might affect the color some. The sides and bottom of the tub, which are light tan vinyl appear to be stained, and the underside of the lid was clearly stained where it contacted the water. When I wiped the underside of the lid with a white terrycloth rag, some but not all of the stain wiped off leaving stains on the cloth. The color of the stains look yellow brown to me and brownish green to my wife. The filter cartridges which were put in clean yesterday were extremely dirty, mottled with dark brown substance which appears to be water soluble and/or easily sprayed off. I think the cartridges will clean up completely, although I haven't done so yet.


The only things that differ from previous fills is that the boric acid is from Florida Laboratories instead of from Duda Diesel, and that I added more dichlor to get the CYA up right away, and then used hydrogen peroxide to neutralize the chlorine. I did a similar process about six weeks ago, at Matt's sugestion, when I was trying to neutralize combined chlorine, and at that time there was no discernable side effect.


I can't believe that this was an algae bloom in fresh water that had been super chlorinated, and then left covered to heat at 66 deg F with 3.5 FC. I'm guessing that it is due to some type of chemical reaction, but I can't imagine what.

I've attached some pictures. The tub, the filters next to a clean filter, and the inside of the lid. You can just barely see the stain on the inside of the lid.

Just before writing this post, I added chlorine up to about 20ppm to see what would happen.

Any thoughts would be appreciated.

thanks,

Michael
 

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domct203

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Jun 3, 2015
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That looks like iron that has come out of solution from the high FC levels. Have you had the well checked for iron levels?
 

MPurcell

Well-known member
Feb 17, 2017
105
Dahlonega, Georgia
I don't know if iron content in a well can change over time, but when I first set up the tub in February, I had the water tested with results of copper 0.1 ppm and iron 0.1 ppm. I didn't even purchase a hose end filter like you can get because the readings were so low, and I have previously had no issues.

As I mentioned in the OP, right before sitting down to write the post yesterday afternoon, I super-chlorinated the water again to approx 20 ppm FC, just to see what would happen. Gradually over the next few hours the color precipitated out and was caught in the filters. By bedtime, the water was pretty clear, and by this morning it was completely clear. It turned three sets of filters completely brown, and a fourth set a little bit brown. The staining on the inside of the lid seems to be permanent, though, and there is just a slight bit of staining left on the under water surfaces of the vinyl, even after I scrubbed them with a white doodle bug pad.

It seems all is well for now, but I'd still like to know why it happened.
 

domct203

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LifeTime Supporter
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Jun 3, 2015
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From everything you described, this does indeed sound like iron.

I don’t know if the iron levels will change with the seasons, but the test from February could have been wrong.
 

MPurcell

Well-known member
Feb 17, 2017
105
Dahlonega, Georgia
The consensus seems to be "iron" although we have never had any indication of excessive iron, as in deposits in the toilet bowl, etc. I had the fill water tested at a local pool store which has one of those electronic testing setups. The other parameters they gave me were pretty close, pH 6.4, TA 10, CH 15. Those are pretty much right on, based on my own subsequent testing, and what it takes to bring the levels up to where they should be. The water here in Georgia, even in Atlanta where we lived once upon a time, is pretty soft and I've never heard of iron problems around here, although as you know, the soil is red not black.

I'm not sure where I would take the water for testing to get accurate results. Lab testing would likely be a bit pricey. So I guess I'll just live with not really knowing for sure. Anyway, we used the tub last night, and the water was beautiful. Having zero CC was nice for my wife especially, as her nose and face didn't itch.
 

domct203

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Jun 3, 2015
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It's the high chlorine level that forces the iron out of suspension and makes it visible, as in the form of yellow water and rusty filter cartridges. Unless you are maintaining a very high FC level in your toilet bowl, you will most likely not see iron deposits there with the low levels you posted.


BTW- The 'electronic testing setups', if not routinely & properly cleaned & calibrated, can be more trouble than they are worth as far as accurate testing is concerned. You have the proper testing equipment with your K-2006, trust your testing.

Glad you were able to enjoy that tub last night! :paddle::paddle: Yes, low, to no CC's, coupled with pH in the proper range, will do wonders for bather comfort.
 

MPurcell

Well-known member
Feb 17, 2017
105
Dahlonega, Georgia
When I first set the tub up in February, (when I was also a complete newb to water chemistry,) I had pre purchased all the supplies for bromine but had failed to purchase any sodium bromide to build the bromide bank. I read that you can crush a few BCDMH tablets to get enough bromide into the water to start, so I crushed up five of the BCDMH tabs and threw them into the tub. Immediately, the water turned yellow brown just like this time, and diminished over less than a day, getting caught in the filters in exactly the same way. At the time, after doing some research, what I believed had happened was that the bromine level got so high that free elemental bromine was formed which has a yellow brown color. For the intervening time I have thought that was what had happened. Now, it appears that that incident was also iron forced out of suspension by high sanitizer. I never did notice any staining in that case though, but the cover was never put on it when it was discolored.

I ran the bromine tub for six months before refilling. Then when I did drain and refill and switched from bromine to chlorine, I made a mistake with the dichlor, putting in more than I was intending to by a factor of 10 (those pesky decimal points!) Afterwards I calculated approx 100 FC and about 90 CYA, so I had to drain about 90% of the water and refill again to get the CYA level down. The interesting thing is that in that case, the water did not turn color. Further, on that fill, which had never turned color, when I later began noticing a problem with high combined chlorine, at Matt's suggestion, I super chlorinated to see if it would reduce the CC's. The water did not turn color in that case either, but I don't think the chlorine got above 20 ppm in that instance.
 

orion6192

Well-known member
Sep 9, 2016
45
Wayland
When I first set the tub up in February, (when I was also a complete newb to water chemistry,) I had pre purchased all the supplies for bromine but had failed to purchase any sodium bromide to build the bromide bank. I read that you can crush a few BCDMH tablets to get enough bromide into the water to start, so I crushed up five of the BCDMH tabs and threw them into the tub. Immediately, the water turned yellow brown just like this time, and diminished over less than a day, getting caught in the filters in exactly the same way. At the time, after doing some research, what I believed had happened was that the bromine level got so high that free elemental bromine was formed which has a yellow brown color. For the intervening time I have thought that was what had happened. Now, it appears that that incident was also iron forced out of suspension by high sanitizer. I never did notice any staining in that case though, but the cover was never put on it when it was discolored.

I ran the bromine tub for six months before refilling. Then when I did drain and refill and switched from bromine to chlorine, I made a mistake with the dichlor, putting in more than I was intending to by a factor of 10 (those pesky decimal points!) Afterwards I calculated approx 100 FC and about 90 CYA, so I had to drain about 90% of the water and refill again to get the CYA level down. The interesting thing is that in that case, the water did not turn color. Further, on that fill, which had never turned color, when I later began noticing a problem with high combined chlorine, at Matt's suggestion, I super chlorinated to see if it would reduce the CC's. The water did not turn color in that case either, but I don't think the chlorine got above 20 ppm in that instance.

I had the same experience as you, even the filters getting discolored - although I was not switching from Bromine. Here was my journey: SOLVED: Hot Tub Green Water Color Issue After Clean Fill - Fixed with Ahh-Some!

After a few purges and then using the maintenance does weekly, I just flushed my tub yesterday before winter and still have completely clear water.

Hopefully this will help - I had some pretty nasty stuff come out even though I religiously keep my tub balanced and sanitized and flushed it with SeaKlear. Not anymore - AhhSome all the way. Everytime I empty twice a year. Ahhsome the night before, drain, wipe, fill, add 15ppm bleach for 20mins, dump, refill, add 1oz metal removal liquid and then dry acid and 50pmm borates in the form of GentleSpa.

Scott
 

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