CYA dilution discussion

[UnderWaterVanya]

Split off from the topic "CYA is over 100" in testing and balancing. Please remember to keep very complex or technical discussions separate from new member's threads. Thanks! Zea3
CYA testing trick:

If it reads over 100. Don't toss out the solution you mixed... Dilute it and retest.

Add one part tap water and one part of your mixed solution of reagent and pool water. Redo the test and multiply the result by 2.

You can even go one step further if that reads to high. Take the dropper bottle Abd fill with the 50/50 solution. Poor into another vial/cylinder. Add enough tap water to reach the label like you do when mixing the normal solution. Then dump this into the vial with the already diluted solution and mix them. This results in 2:1 dilution and the result is tripled.

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[y_not]

Re: CYA is over 100

You can even go one step further if that reads to high. Take the dropper bottle Abd fill with the 50/50 solution. Poor into another vial/cylinder. Add enough tap water to reach the label like you do when mixing the normal solution. Then dump this into the vial with the already diluted solution and mix them. This results in 2:1 dilution and the result is tripled.

UWV, I know what you're describing here, a 2:1 dilution. Easy peasy.
But I have to say, I got horribly confused reading this the 1st time. In regards to pouring it into another container and such. I had to read it 2x and still, I was drawing a bit of a HUH??
It finally made sense the 3rd time, later in the day.
I already know how to do this, it's basic science. But a new TFP'er reading this might not.

Are you just simply saying to put it all in another container, say a glass Pyrex measuring cup. Then add as much tap water as you have solution. Then pour it all back into the mixing bottle till you fill it, cap it, shake it, then proceed with the test and multiply by 3?
I might then ask, why not just pour it into the mixing bottle to measure the fluid amounts, just as you did with the initial test?

Pour the already diluted 1:1 /w tap water (pool water+cya solution) to the bottom of the line/label of the mixing bottle. Then add tap water to the top, right where it begins to taper up to the nipple. Shake it up, then proceed with squirting it into the CYA graduated tube.
I would think there'd be a lot less room for error in the dilution this way. Beats fighting with measuring cups, or guessing on the dilution.

Just wondering if it could be made simpler, or if it's just my abstract brain.

 

[Richard320]

Re: CYA is over 100

When I had to deal with astronomical CYA, I'd mix my pool sample with tap water in the CH/TA vial. It's already graduated nicely. Then I'd swirl that a bit to be sure it was mixed, pour that sample into the CYA mixing bottle to the line, then add the CYA reagent. The result got doubled.

 

[UnderWaterVanya]

Re: CYA is over 100

Actually if you do what you describe then you end up with 3 parts tap water to 1 part pool water... And a 4x multiplier unless I misread you.


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[UnderWaterVanya]

Re: CYA is over 100

When I had to deal with astronomical CYA, I'd mix my pool sample with tap water in the CH/TA vial. It's already graduated nicely. Then I'd swirl that a bit to be sure it was mixed, pour that sample into the CYA mixing bottle to the line, then add the CYA reagent. The result got doubled.

I agree but if you have the Taylor kit with limited CYA reagent this is a way to conserve reagent.

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[y_not]

Re: CYA is over 100

Actually if you do what you describe then you end up with 3 parts tap water to 1 part pool water... And a 4x multiplier unless I misread you.

This?

Pour the already diluted 1:1 /w tap water (pool water+cya solution) to the bottom of the line/label of the mixing bottle. Then add tap water to the top, right where it begins to taper up to the nipple.

If so, that's only diluting it twice from the original sample. Which is 1/2 pool water, 1/2 melamine solution. Which is still too high. So you dilute that, test, still get too high. So you dilute again. Is that not 2:1? Or are my math skills, or lack thereof failing me? :?

 

[chem geek]

Actually if you do what you describe then you end up with 3 parts tap water to 1 part pool water... And a 4x multiplier unless I misread you.

The CYA test already mixes half sample water with half melamine solution (which has a lot of water) and the tube is calibrated for that so you do NOT count this 50/50 in terms of any multiplier.

So if you do a 50/50 dilution of the sample before you then do a 50/50 mix with the melamine solution, that's just a 2x multiplier -- you only count the dilution of the sample BEFORE mixing with an equal volume of melamine solution.

As noted, the above technique lets one measure >100 ppm CYA, but does not save on melamine reagent, but you want to be careful about using less since there may be only enough melamine to bind with somewhere above 100 ppm CYA but who knows how much. So if you plan on using less melamine solution, then use a smaller sample size as well, but make sure the sample gets separately diluted so that you read roughly 50 ppm CYA or less.

 

[UnderWaterVanya]

Re: CYA is over 100

IOriginal is 1:1 but we call it "normal".

Dilute the "normal" with an equal part of tap water gives a solution that is 3 parts tap water, 1 part melamine. But the important part is that this is 1/2 the concentration you started with. Original was 1/2 (1 part melamine in 2 total parts), 1/2 x 1/2 = 1/4 which is what the equal parts of the original "normal" and tap water solution makes.

So far so good.

Now to get to something that measures three times the CYA you need something that has 1/3 as high of a concentration of melamine as the "normal". 1/2 x 1/3 = 1/6 which is five parts tap water 1 part melamine.

Alternately you can take your already diluted 1/4 solution and turn it into a 1/6 solution. 1/4 x 2/3 = 1/6. The easy way to make this is to combine 2 parts of the current solution (a full dropper bottle) and add a half bottle of tap water. Alternately you measure a set amount of the current 1:4 solution and add half as much tap water.

I typically don't break down the precise mix of melamine because it confuses the CYA math. Essentially you take the inverted fraction and divide by two to get your CYA multiplier. If you deal in fractions of the "normal" solution the you merely invert the fraction.

Now do you see why if you take the "normal" solution and dilute with equal parts of tap water resulting in a 1/4 solution and then dilute it again with equal parts water and the current concentration you end up with a 1/8 solution (1 part melamine, 7 parts water) which measures 1/4 the actual CYA so you would multiply any result by 4 not 3.

I need to take the time to explain it graphically I suspect it would be easier than all these words.

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[y_not]

Re: CYA is over 100

OMG!!!!
I feel like I'm in math class again. UUUGGGHHHH!!!

I'l have to try to process this tomorrow when I'm not as sleepy.
I appreciate the explanation, it's just that my eyes glaze over when I see math. I can do it quite well once I learn it, but learning it and keeping it there is a challenge. Which is far from an intellect issue, but more of an attention issue. HA

I'll do me best to figure it out.

 

[Swampwoman]

Re: CYA is over 100

For the OP, to simplify all this, just put pool water to the 7 ml mark on the bottle. Add tap water to the next line on the bottle. Shake. Now carefully discard half the solution until your back to the 7 ml mark. Now add the cya agent from the bottle to the next line. Shake. It it's not 70 degrees, let it warm up in the house. Then do the reading. Multiply your answer by 2. If you're still over 100 before you multiply by 2, you'll have to resort to further dilution per the above conversations.
But for your purposes right now, this will be less overwhelming, I suspect -- you can buy big bottle of replacement cya agent cheaply, btw. You may wish to do so while getting this issue sorted.

One thing I want to tell you because you said you'd gotten ad at your pool and let it go....once you read up in pool school, you'll quickly see that while getting things sorted the first time is a pain in the butt, you and your pool will soon become dear friends An ounce of prevention is a pound of cure! In other words, if you always maintain the proper cya-to-chlorine levels, you'll never have to wrangle with your pool again!

So hang in there, even if you feel overwhelmed.

If you haven't owned a pool before, and if you can afford it, you might want to pay a pool company to close it for the winter (if you decide you want/need to) and to show you what to do and why. It's easier to see someone do it than to try to visualize it from written word. Once you see what they're doing, then the written descriptions make more sense.

So, your options are:
1. Close it as is...yourself or by pool co., and read up on pool school over winter...sometimes, cya goes down over winter due to a bacteria that forms and eats it.

2. Drain partially (eg 50 percent) and refill to get cya down, possibly do this twice if you intend to go through the shock process now or leave it open through the winter. You need the cya down in order for the chlorine used in shocking to work right.

Once you decide which way to go, let us know and we can help you map out next steps. If you want to close and do it yourself, there are threads on how to do so.

Welcome and best wishes!

 

[UnderWaterVanya]

Re: CYA is over 100

For the OP, to simplify all this, just put pool water to the 7 ml mark on the bottle. Add tap water to the next line on the bottle. Shake. Now carefully discard half the solution until your back to the 7 ml mark. Now add the cya agent from the bottle to the next line. Shake. It it's not 70 degrees, let it warm up in the house. Then do the reading. Multiply your answer by 2. If you're still over 100 before you multiply by 2, you'll have to resort to further dilution per the above conversations.

Did you mean add CYA reagent or tap water in step two? Your solution as typed is 3 parts melamine, 1 part tap water. Which would overestimate CYA. Doing it as you described but adding tap water in the last step would give the right mix for a solution that reads 1/2 the actual CYA level.

Mods, maybe we could pull these posts into the deep end? I'll do some drawings and post them in the deep end if this gets pulled out to there.


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[UnderWaterVanya]

Thank you mods

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[Swampwoman]

I was simply describing this, per ChemGeek:

So if you do a 50/50 dilution of the sample before you then do a 50/50 mix with the melamine solution, that's just a 2x multiplier -- you only count the dilution of the sample BEFORE mixing with an equal volume of melamine solution.

I was worried that a poster who hadn't added chlorine for 2 months might have been overwhelmed by the open discussion on dilution, so was attempting to bring it back to a simple step by step instruction

 

[kacreech]

Would it be ok to leave the pool as is and just keep running the pump all winter and deal with the CYA in the spring?

 

[UnderWaterVanya]

I was simply describing this, per ChemGeek:

So if you do a 50/50 dilution of the sample before you then do a 50/50 mix with the melamine solution, that's just a 2x multiplier -- you only count the dilution of the sample BEFORE mixing with an equal volume of melamine solution.

I was worried that a poster who hadn't added chlorine for 2 months might have been overwhelmed by the open discussion on dilution, so was attempting to bring it back to a simple step by step instruction

But what you posted isn't this. You posted a solution that was 1 part melamine and 1 part pool water, which you then dumped out half, and added another 1 part of just melamine - that's backwards. You need to add tap water after dumping out half the melamine solution.

I think... now you have me confused! LOL

 

[UnderWaterVanya]

Would it be ok to leave the pool as is and just keep running the pump all winter and deal with the CYA in the spring?

Yes.

 

[y_not]

Mods, maybe we could pull these posts into the deep end? I'll do some drawings and post them in the deep end if this gets pulled out to there.

Thanks for suggesting that UWV, I was too tired last night to even think about that. HAHA

Would it be OK to leave the pool as is and just keep running the pump all winter and deal with the CYA in the spring?

kacreech,
I would suggest resuming with your regular questions back in the original thread where it pertains to all the details of your pool, instead of our CYA discussion. We were bad.... We should have done it here in the 1st place. So we split this here to discuss the intricacies and more complex details of the dilution process. Since we were getting a little too complex for the new TFP member area.
Basically we're having a "nerd" debate and it's probably going to get even more complex.
We all still have that thread in our notification list, so we'll see your new posts when they come through.

 

[Swampwoman]

Uwv, I posted a solution that was 50/50 pool and tap water, shaken, then reduced back to the 7 mil, then added another 7 mil cya solution, per ChemGeek:

this, just put pool water to the 7 ml mark on the bottle. Add tap water to the next line on the bottle. Shake. Now carefully discard half the solution until your back to the 7 ml mark

 

[UnderWaterVanya]

Somehow I missed that you were mixing the sample water with tap before the reagent was added.

The goal I was working from all along was how to react to a high reading without wasting more reagent. Once the CYA SMS melamine react you can water down the solution to make it measure higher CYA without using more melamine. At least that is what chem geek told me.

It is much simpler to dilute the sample water when you know that you are dealing with a high CYA. That method is much easier to explain and teach. But if the goal is to conserve the melamine after you tested and found you have over 100 CYA, then you could save reagent by diluting the already reacted solution the way I was describing things.

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[chem geek]

Yes that is correct. You can either dilute the water sample before mixing or you can dilute it afterwards though there is the risk in this latter case that there isn't enough melamine to react with all the CYA if it is very high. It depends on how much excess of melamine there is to handle CYA beyond 100 ppm. There's probably enough for 200 ppm or so given what people report about the black dot disappearing below the 100 ppm line, but I don't know if there's enough for much more than that.