Ok took the pool store a sample to see if my testing is accurate. I was right on about TA. It was at 40. I was close on chlorine. I thought it was 4 and it was 5. CYA is still 50....as it should be since I do not use Tri-Chlor anymore. I had the pH at somewhere between 7.4 and 7.6. It was at 7.3. So I am going to try and lift that stain first with Oxa...something acid pack. If that doesnt work I will try Absorbic which seems expensive. I am also going to try and get the TA up. Its getting lower and lower.
Newbie with too high CYA
- Thread starter mustang68
- Start date
mustang68 said:
That little bag that I bought at the pool store had no effect. This stain has to be copper or iron. It is brown, in a circle swirling pattern and sits right in the middle just below the intake ports at the deep end of the pool. Anyone else have any ideas?
To see if the stain is iron, drop a Vitamin C tablet on it. If that makes a hole in the stain, then go ahead with the ascorbic treatment. If the C tablet does nothing, it's not iron, and the next experiment would be to drop a trichlor tab on it.
--paulr
--paulr
PaulR said:
Thanks I'll try that. I just had a new issue. Since I used that Oxylic (?) acid pouch I had to raise pH substantially to get my Ta above 30 where it had been sinking to over the last week and a half. I used the calculator and put in the recommended amount of sodium bicarb. Worked great. TA went to 100 and holding. pH is now 7.6. My FC had been 5 since I took the sample to the store. Well since the pack I tried and the bicarb I used to get the TA up my FC is now 0.6 :?
The calculator calls for 71 ounces of my 10% bleach so I'm doing that in 3 doses over the next couple of hours. I have no idea how this happened. I tested twice in diff spots to be sure and the same thing.
That would be oxalic acid. I did some quick web searching and it is sometimes used as a stain preventer. It will lower your pH a lot, as you found. Also it seems that it is consumed by chlorine, that's why your FC disappeared, looks like you should get the FC down first before using it. And then bring FC up slowly afterward.
I think really the first step is to be sure what the stain is, then you'll know what treatment to try. The Vitamin C test will tell you if it's metal. If not, drop a chunk of trichlor on it, if that works it's an organic stain and more chlorine will clear it up. (If neither of those work, I'm out of ideas.)
--paulr
I think really the first step is to be sure what the stain is, then you'll know what treatment to try. The Vitamin C test will tell you if it's metal. If not, drop a chunk of trichlor on it, if that works it's an organic stain and more chlorine will clear it up. (If neither of those work, I'm out of ideas.)
--paulr
PaulR said:
Its a start. Thanks. My chlorine is up to 4 and I have one more dose to go so it will be fine by tomorrow if that acid doesnt drag it down again. If it does the fix seems simple. Keep dosing it with bleach until its stable at 6. Where do I get a big dose or tablet of Vitamin C? Also I never have had a CC issue. Will this introduce that?
Any grocery store or drug store will have Vitamin C, as long as it's in tablet form you can use that for the experiment. Whether a bottle of tablets would be enough to eliminate the whole stain, I don't know. I've never had to do this myself, and my impression is you usually dose the whole pool which requires fairly hefty quantities. I suppose if the experiment works, and you have only the one spot, you could try dumping a bottle of tablets on the stain and see if it all clears up.
I can't remember if these processes produce CC, my intuition is that they would not, but then my last attempt to learn any chemistry was 30 years ago. And as I said I've never done this myself. You should do some research on this process, about all I can do is tell you what experiments people do to figure out what the stains are.
--paulr
I can't remember if these processes produce CC, my intuition is that they would not, but then my last attempt to learn any chemistry was 30 years ago. And as I said I've never done this myself. You should do some research on this process, about all I can do is tell you what experiments people do to figure out what the stains are.
--paulr
Ascorbic Acid (and oxalic acid, for that matter) is a reducing agent so chlorine will oxidize it with the net result that the chlorine will drop. This is why you usually let the FC level drop before adding Ascorbic Acid because the Ascorbic Acid is expensive while the chlorine is relatively cheap. You should not see any increase in Combined Chlorine (CC) when using Ascorbic Acid. You probably should use an algaecide, such as PolyQuat 60, while the FC is zero so that you help prevent algae growth.
Note that I am referring to a whole-pool Ascorbic Acid treatment. If you are just putting Ascorbic Acid in a jar put over a local stained area of the pool, then my comments wouldn't apply -- the chlorine would get used up locally, but the excess of Ascorbic Acid would usually lighten the stain if it were iron (and may lighten it if it were copper).
Note that I am referring to a whole-pool Ascorbic Acid treatment. If you are just putting Ascorbic Acid in a jar put over a local stained area of the pool, then my comments wouldn't apply -- the chlorine would get used up locally, but the excess of Ascorbic Acid would usually lighten the stain if it were iron (and may lighten it if it were copper).
chem geek said:
Thanks guys. The Vit-C worked to lighten the stain but its to big to treat with this approach. Its the size of a basket ball so I will wait for the FC to drop some on its own and when its low enough I will do the whole pool. I see a few other small spots on the side walls, which seems strange. I would think the metals would drop and be more on the floor than on the sides.
When metal ions are dissolved in water, they are just like other ions (e.g. salt) and won't settle to the bottom so the stains can be anywhere, usually where the circulation is a little less vigorous and where the surface material is for whatever reason more conducive to staining.
How often do I need to shock the pool if I keep the FC level at my adjusted CYA level? For me thats 6. I have heard never and then every couple of weeks.
If you properly maintain the appropriate FC/CYA level for your pool, then you don't need to regularly shock unless there is an unusual event such as a fecal accident or a dead animal. Also, if there is high bather load or something getting dumped into the pool resulting in Combined Chlorine (CC) that you want to get rid of more quickly, then you can also shock, though usually just waiting a day or two results in the CC dropping back to normal (<= 0.5 ppm).
chem geek said:
Thats what my common sense told me but I thought it best to ask anyway. So far all is well. I am waiting on taking on that stain closer to Spring. Then of course I am battling the 1 billion leaves that seem drawn to my pool.