A discussion of CYA turbidity

[Hal3]

That one guy drained his whole pool..... and we had no idea what his CYA actually was!

It looks like I did need to drain the pool after all. CYA increases from turbid water are at most 10 -20 CYA numbers as best as I can tell from this discussion. I was 100+ for CYA.

It was high on the test strip too, come to think about it.

The pool looks great today!!!!

I will continue with by BBB saga back on the original thread.

Bye

 

[frustratedpoolmom]

That one guy drained his whole pool..... and we had no idea what his CYA actually was!

It looks like I did need to drain the pool after all. CYA increases from turbid water are at most 10 -20 CYA numbers as best as I can tell from this discussion. I was 100+ for CYA.

It was high on the test strip too, come to think about it.

The pool looks great today!!!!

I will continue with by BBB saga back on the original thread.

Hal, No offense intended by my remark, hope your not upset with me.... :-D

I do think your CYA was too high and water replacement WAS a good idea. I was surprised that you drained the WHOLE thing....but you control your pool and make the decisions you feel are best for your situation. We just offer our opinions, for what they're worth... I'm glad the pool looks great!!!

Richard, you lost me after "First of all"....

 

[ivyleager]

Richard, you lost me after "First of all"....

He had me at hello............

 

[chem geek]

Hey, Richard,

Assume you have sample (pool) water that was so murky it measured 20ppm in the view tube prior to adding R-0013.

You also knew that the calculated amount of CYA you put in the pool was 40ppm.

When you add the CYA reagent to that sample, do you feel the test would return 60ppm?

Yes that is correct, but measurement errors are pretty large so would be higher when trying to combine two measurement together -- worst case error is doubled so if each single measurement is +/- 10 ppm then the two measurements are +/- 20 ppm. Also, this assumes no interaction between the murky pool water and the CYA test (i.e. they are assumed to be independent and not enhancing each other except for their combined turbidity).

 

[JasonLion]

I figure the higher CYA in a SWG pool would lend itself better to the dilution. Even 50ppm is probably enough though. You should see two 25ppm samples with 50% dilution. Lower CYA might result in diluted samples that wouldn't register on the comparator.

The challenge with this approach to testing is finding dilution water with an appropriately high turbidity. Visibility in a pool with a full algae bloom is very limited. I am not sure where to get a water sample with the correct turbidity (short of letting my pool get algae), and without that this test isn't meaningful.

 

[duraleigh]

Also, this assumes no interaction between the murky pool water and the CYA test (i.e. they are assumed to be independent and not enhancing each other except for their combined turbidity).

Yeah, I understand that. I suppose you could do a standard CYA test on murky water (with no CYA) to see if the turbidity increased without the presence of CYA but that really seems like a stretch. If the reagent reacts with something other than CYA in the water (implying the existance of CYA) wouldn't that invalidate the standard CYA test to begin with?

The challenge with this approach to testing is finding dilution water with an appropriately high turbidity. Visibility in a pool with a full algae bloom is very limited. I am not sure where to get a water sample with the correct turbidity (short of letting my pool get algae), and without that this test isn't meaningful.

Well, the "appropriate high turbidity" sort of gets back to my original thought in this thread. We were saying, "If your pool water is cloudy, the CYA test is invalid"...without qualification. My point is that most cloudy pools aren't cloudy enough to register in a standard CYA test.

So, if we suspect the pool water is turbid enough to affect the outcome of the test, why couldn't we simply put the pool water in the view tube without the reagent and take that reading. Then add the reagent to the pool water and run the test normally. If pool water alone gave you a 20ppm reading and then the standard CYA test gave you an 80ppm reading, you could generally assume your CYA was in the 60 range.

My original thought was cloudy pool water seldom, if ever, gets cloudy enough to give you a 20ppm reading without reagent. That would mean any black object you placed in the pool would disappear when held around 4" underwater. (4" being the depth of water in the view tube to measure 20ppm).

As with anything, there can be extremes. I'm sure there are some pools somewhere that could be murky enough to affect the test but they would, IMO, be pretty hard to find. So, that brings me back to my original thought that we may be using "cloudy pools affect your CYA test" way too much.

 

[SeanB]

...sort of gets back to my original thought in this thread. We were saying, "If your pool water is cloudy, the CYA test is invalid"...without qualification. My point is that most cloudy pools aren't cloudy enough to register in a standard CYA test.

So, if we suspect the pool water is turbid enough to affect the outcome of the test, why couldn't we simply put the pool water in the view tube without the reagent and take that reading. Then add the reagent to the pool water and run the test normally. If pool water alone gave you a 20ppm reading and then the standard CYA test gave you an 80ppm reading, you could generally assume your CYA was in the 60 range.

My original thought was cloudy pool water seldom, if ever, gets cloudy enough to give you a 20ppm reading without reagent. That would mean any black object you placed in the pool would disappear when held around 4" underwater. (4" being the depth of water in the view tube to measure 20ppm).

As with anything, there can be extremes. I'm sure there are some pools somewhere that could be murky enough to affect the test but they would, IMO, be pretty hard to find. So, that brings me back to my original thought that we may be using "cloudy pools affect your CYA test" way too much.

Makes sense to me. I think that's a good recommendation to addopt as a "guidline" while clearing a cloudy pool. Do a viewtube reading with no reaagent and record the number, do it a second time WITH reagent and sbutract the off-set from the first reading from the second test for an apporximate cya reading. It's better than shooting in the dark when trying to determine how much chlorine you need to use.

Good job Dave!

 

[frustratedpoolmom]

...sort of gets back to my original thought in this thread. We were saying, "If your pool water is cloudy, the CYA test is invalid"...without qualification. My point is that most cloudy pools aren't cloudy enough to register in a standard CYA test.

So, if we suspect the pool water is turbid enough to affect the outcome of the test, why couldn't we simply put the pool water in the view tube without the reagent and take that reading. Then add the reagent to the pool water and run the test normally. If pool water alone gave you a 20ppm reading and then the standard CYA test gave you an 80ppm reading, you could generally assume your CYA was in the 60 range.

My original thought was cloudy pool water seldom, if ever, gets cloudy enough to give you a 20ppm reading without reagent. That would mean any black object you placed in the pool would disappear when held around 4" underwater. (4" being the depth of water in the view tube to measure 20ppm).

As with anything, there can be extremes. I'm sure there are some pools somewhere that could be murky enough to affect the test but they would, IMO, be pretty hard to find. So, that brings me back to my original thought that we may be using "cloudy pools affect your CYA test" way too much.

Makes sense to me. I think that's a good recommendation to addopt as a "guidline" while clearing a cloudy pool. Do a viewtube reading with no reaagent and record the number, do it a second time WITH reagent and sbutract the off-set from the first reading from the second test for an apporximate cya reading. It's better than shooting in the dark when trying to determine how much chlorine you need to use.

Good job Dave!

I like that idea better than the coffee filter...not everyone is a coffee drinker and has filters on hand...(I know I don't. )

 

[Guest]

There is another possibility and that is that water with algae in it has many more particles for nucleation of precipitate so *maybe* the CYA test gets a non-linear effect in CYA ppm apparent concentration by having the CYA clump more readily onto algae rather than be dispersed in the "standard" that occurs from shaking it for 30 seconds. Maybe that reduces transmission more than would be accounted for independent concentration alone. That's just pure speculation on my part.

Richard

I have speculated the same thing myself and until this can be conclusively discounted I feel it needs to be kept in mind as a distinct possiblility.
If you want this in layman's terms, it means that the tiny specks of algae floating in the water might interfere with the CYA test and cause precipitation to happen to a greater extent by 'seeding' the sample in a similar way to how clouds are seeded with tiny particles to help produce more rain than would otherwise occur.

 

[SeanB]

Seems like we've gone all the way back around again.

Just to clarify, I think the essential thing to get from this thread is this:

As a "guidline" while clearing a cloudy pool - Do a viewtube reading with no reaagent and record the number, do it a second time WITH reagent and subtract the off-set from the first reading from the second test for an apporximate cya reading. It isn't perfect but should give a fair approximation.

I think this simple method will be a big help to pool owners who need a cya guestimate in a cloudy pool.

If anyone cares to continue the discussion / debate, please start a new thread. I'm going to close this one just so we don't dilute, or lose site of, what has been learned so far.

I'm happy to split out any posts that you may want in a new thread.

Thanks,
Sean