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Cyanuric Acid 200ppm - Drain Pool? - Swimming Pool Help

Cyanuric Acid 200ppm - Drain Pool?

What is floc, clarifier, stabilizer, cyanuric acid, algaecide, brightener, dichlor, sodium hypo, sodium bisulfate, and others???

Cyanuric Acid 200ppm - Drain Pool?

Postby kristymcj » Wed 01 Apr, 2009 21:43

Shocked pool, then added chlorine pucks. Pool store test says there's no chlorine. Also, PH is always too low, even with Alkalinity adjuster and Baking Soda.
Pool store uy say to replace 68% of the water. True?

Free Chlorine: 0 ppm
Total Chlorine 0 ppm
Combined Chlorine 0ppm
PH 6.4
Hardness 350 ppm
Alkalinity 70 ppm
Cyanuric Acid 200 ppm
Copper 0
Iron 0
TDS 1700 ppm

More details: above ground pool, installed 1988. Pool looks pretty clear (was green before shock).Running sand filter all the time.
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Cyanuric Acid 200ppm - Drain Pool?

Postby chem geek » Wed 01 Apr, 2009 23:29

Yes, true, assuming the pool store's measurements are correct. What did you use for shocking the pool -- that is, what product (what does it say in the ingredients)?

Since it's an above ground pool, you need to be careful about draining it and either need to do a continuous drain/refill which uses more water or you can do multiple partial drain/refills or can use the sheet or silage bag method (drain from under the sheet or outside the silage bags and fill above the sheet or inside the silage bags).
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Cyanuric Acid 200ppm - Drain Pool?

Postby kristymcj » Thu 02 Apr, 2009 01:24

The shock was Super Zappit calcium hypochlorite. Thanks for the info. I'm looking into the drain options you mentioned now.
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Cyanuric Acid 200ppm - Drain Pool?

Postby Larry » Thu 02 Apr, 2009 01:49

Calcium hypochlorite is suitable for shocking the pool, though it does increase the calcium hardness level. The absence of chlorine is due to the green water "using up" all the chlorine you added. It probably still needs a whole lot more chlorine to satisfy the chlorine demand.

Chem geek asked about the type of chlorine as he may have suspected you were using a stabilized chlorine product (dichlor or trichlor) as a shock. The high cyanuric acid level could indicate this.

The sooner you get the partial drain/ refill done, the better. If you can do it soon then you will save on chemicals as you will only shock again once the refill is done. Also consider chlorinating liquid (or bleach) that will not affect the stabilizer or hardness levels.

You will also need to raise your alkalinity and pH, but wait till the fresh water is in, test again and then post your results here.

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Cyanuric Acid 200ppm - Drain Pool?

Postby Me... » Thu 02 Apr, 2009 08:54

Shocking/chlorinating with Liquid for a bit will raise that pH also.
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Cyanuric Acid 200ppm - Drain Pool?

Postby chem geek » Thu 02 Apr, 2009 11:26

True, at least until the chlorine level comes back down. However, with his numbers, I get that even adding hypochlorite chlorine of 20 ppm FC would only increase the pH from 6.4 to 6.47 mostly because the pH buffering is very strong at lower pH (and he's got buffering both from carbonates and from CYA).

Also, low pH is the most destructive factor for vinyl so since this is an above ground pool I'd get the pH up to at least 7.0 or 7.2 even if one is going to be shocking with chlorine. To get the pH up with less of an increase in TA, one can use 20 Mule Team Borax instead of pH Up (Arm & Hammer Super Washing Soda) or one can try aeration of the pool water (and remove any Trichlor in the pool). Kind of a shame to add it and then do a partial drain/refill, but I certainly wouldn't wait too long to get this pool into shape. On the other hand, really bad damage to pools using Trichlor with no adjustment to pH often has them with 0 TA and a pH of 4-5 so it could be worse.

I calculate that to get to a pH of 7.0 it would take about 15-1/2 pounds of Borax in 10,000 gallons, or around 3-1/3 76-ounce boxes in 10,000 gallons. The TA would rise to about 120 ppm after doing this. One should add half this amount, just in case the pH or other readings aren't correct, and then retest.

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Cyanuric Acid 200ppm - Drain Pool?

Postby kristymcj » Thu 02 Apr, 2009 12:38

The instructions said not to drain more that 20% of the water at a time. Am I right in assuming that the best way to go about this is to drain 20% of the water and re-fill 3-4 times?
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Cyanuric Acid 200ppm - Drain Pool?

Postby chem geek » Thu 02 Apr, 2009 13:28

Yes. Each partial drain/refill of 20% of the water will dilute the CYA as follows: 80%, 64%, 51%, 41%. So after doing this 4 times and starting with 200 ppm CYA you'll end up with around 80 ppm CYA which is still high, but more tolerable. In order to get the most CYA removed, I suggest you drain from near the bottom of the pool. If you can't do that, then be sure to thoroughly mix the added fresh water when added to the pool.
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Cyanuric Acid 200ppm - Drain Pool?

Postby firehall90 » Thu 18 Mar, 2010 19:49

The idea of draining a pool to lower cyanuric acid is a bit outdated. A 40k pool can have this level reduced by 100ppm by adding 2lbs of lye. It will in effect raise the pH, but only slightly and lye can be purchased at most home improvement stores in the plumbing department as a drain unclogger. Only pure lye should be used as any other product will contain additional metals such as alluminum. the ingredient will list 100% calcium chloride if it is ture lye. The same is used in water treatment at plants the utilize isocyanuric acid to stabilize chlorine.
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Cyanuric Acid 200ppm - Drain Pool?

Postby chem geek » Thu 18 Mar, 2010 20:50

firehall90 wrote:The idea of draining a pool to lower cyanuric acid is a bit outdated. A 40k pool can have this level reduced by 100ppm by adding 2lbs of lye. It will in effect raise the pH, but only slightly and lye can be purchased at most home improvement stores in the plumbing department as a drain unclogger. Only pure lye should be used as any other product will contain additional metals such as alluminum. the ingredient will list 100% calcium chloride if it is ture lye. The same is used in water treatment at plants the utilize isocyanuric acid to stabilize chlorine.

What? It is true that a high pH of 9-10 AND high levels of chlorine can oxidize Cyanuric Acid and is sometimes done for water treatment, but this isn't something to be done safely in a pool. The high pH can create calcium carbonate scale and the very high chlorine levels required can oxidize and corrode what is in the pool (including metal).

Lye is just sodium hydroxide (not calcium chloride -- you are thinking of calcium hardness increaser) and raises pH. There is NOTHING special about lye. Any strong base can be used to raise the pH, even 20 Mule Team Borax (sodium tetraborate decahydrate). Adding 2 pounds of lye to a 40,000 gallon pool that has a TA level of 150 ppm with CYA of 100 ppm would raise the pH from 7.5 to 8.9. If the pool was near saturation with calcium carbonate to protect plaster surfaces, the index would get to about +1.5 which would very likely cause scaling.

Also, the CYA will not drop just from high pH alone. It requires either an enzyme-driven pathway or a lot of oxidizer in the water. This scientific paper talks about the biodegradation of CYA by bacteria and this link describes that pathway in more detail, but this isn't a very reliable way to degrade CYA in a pool and it produces a LOT of ammonia that then needs to be oxidized or otherwise removed. This patent describes the oxidation of CYA by chlorine at a pH of 9-10, but it takes a LOT of chlorine to do so -- needing a minimum of 2.5 times as much FC as the CYA you want to eliminate (so 250 ppm FC to get rid of 100 ppm CYA) -- clearly impractical.

Can you please link to specific references for the procedure you describe that so rapidly gets rid of CYA?
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