Fine dust collection, drying, and subsequent direct chemical assay on that fine dust, as dust

Gary Davis

Active member
Aug 29, 2022
29
Modesto, California
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
I ask here in the deep end but please move this if it's still the wrong place to ask this direct chemical collection & assay question.

This isn't a question about pool cleaners other than how to collect in my hand a sample of dust to directly chemically assay, as dust.
Likewise, this isn't a question about testing & balancing water so much as it is a question of identifying the dust in and of itself, as dust.

Nor is this a question about pumps, filtering and plumbing so much as they would work if I wasn't running this test on purpose to obtain the dust, as dust.

I'm not just getting started as I know where and why the dust is most likely coming from so that's not what my question is about.
And it's an old in-ground non-saltwater gunite and plaster pool, so it's not the temporary plaster dust you see just after construction.

If the direct collection and direct chemical assay does turn out to be dead algae, only then would it belong in the algae section, but white is a strange color for algae (tan maybe).
Having thought hard, I couldn't find any other sub forum to ask this in other than everything else or the coffee bar maybe?

So if this is being asked in the wrong place, please move it to the right place to ask how to physically collect & directly assay any given fine pool dust.

Thinking ahead, most replies I'm sure will helpfully ask about the pool chemistry but that's NOT what this question is asking about at all.
I know the pool chemistry always points to the most likely chemical composition of the dust, whether algae, pollen or calcium precipitate.

And in this case, the pool chemistry leans toward calcium saturation (of course), but I am not asking about chemistry so much as about
  • Collection of the fine dust
  • Direct assay of the collected fine dust
Do you have any experience physically collecting a fine dust in your pool deep end that you can explain here?
And/or do you have experience running a direct chemical assay on that dried powdered dust that you collected?

I know the typical questions will ask if I have algae (I don't see any) and if I have the chlorine level high enough over the stabilizer (I do) and if the calcium saturation indicators are within the balanced zone and whether or not I recently added diverse chemicals that would cause an immediate chain reaction clouding (I didn't) and whether or not the water is clear (it is) and whether or not the temperature cooled recently (it didn't), and probably a dozen more questions about water chemistry (mostly about balance) or pool equipment (mostly about the cleaning system).

I know the typical way to identify the dust is the answer to those questions (almost all of which lean toward calcium precipitate) but it still "could" be algae dust (probably not though) and it definitely could be pollen (as I have too many pollinating bees all around the pool as I'm surrounded by close neighbors with pretty plants that's for sure). And there are farms nearby where they sometimes generate clouds of dust that you can taste in your teeth.

With all that as the lead in to the collection, drying and assay question, the question itself is rather simple.
  1. Do you have experience collecting a fine dust at the bottom of the pool and then drying sufficient quantities?
  2. Do you have experience directly running a chemical assay on the dried dust?
How did you do it?
 

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JamesW

TFP Expert
Mar 2, 2011
31,539
Use a skimmer sock in the skimmer with a skimmer vac plate and vacuum the dust.

This will allow you to collect the dust in the sock.

Allow the dust to dry.

One test you can do on the dust is to put a drop of acid on the dust to see if it bubbles, which would indicate calcium carbonate.

Most likely, it’s calcium carbonate from the cement and the aggregate in the plaster if the aggregate is marble.

Marble aggregate is a gritty type of hard sand.

You can put 0.5 grams of the dry dust into 1 liter of distilled water and the TA and CH should increase by 500 ppm if the substance is calcium carbonate and if all of the substance dissolves.

If only some dissolves, the levels will increase accordingly.
 

JamesW

TFP Expert
Mar 2, 2011
31,539
Calcium hypochlorite will often leave this type of dust, so make sure that you don’t use calcium hypochlorite for a while before doing the test.

Dissolving plaster will often cloud while brushing, so that can be a good indicator.

Some cleaners have fine mesh that will collect dust.

Do you have a cleaner other than the in-floor system?

The cartridges will often collect plaster aggregate, so you can see if the cartridges have any aggregate in the pleats as you clean the cartridges.

Maybe clean the cartridges over a fabric that can allow the water to pass through but fine enough to collect any aggregate dust.

If the dust does not dissolve well in distilled water, try putting a drop of acid in the water to lower the pH to see if that makes the dust dissolve faster.
 

Oly

Gold Supporter
Jun 28, 2017
2,763
Fresno, CA
Pool Size
27000
Because we live in the Central Valley and it is the middle of almond harvest season? Dust is in the air.
Suction up a sample of the debris you are seeing and filter the solution through a coffee filter then let it dry. I like to use a 1/2" PVC pipe holding my thumb over the end until over the sample site, then transfer the contents into a container. A diving mask and a turkey baster works too but you may need some diving weights to counter boyancy if in the deep end. Start by using a 10X loop or dissecting scope to look at it. If you want to test it for calcium find a local ag lab and explore your test options.
Also you can run an Overnight Chlorine Loss Test with your test kit to diagnose algae.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
21,044
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Long ago I used my Dolphin robot cleaner with the ultra fine pleated filter to capture lots of fine silt. I rinsed the filter panel into a coffee filter and captured all the fine dust. I let it dry and it was the consistency of talcum powder. I live in the Sonoran desert … dust here comes mainly from fine clay particulates. You can sift the soil here to remove the aggregates and sand and what’s left behind is moldable clay. The Japanese have an art form called durodango which literally means “mud dumpling” … you can mold clay bearing soils into spheres using your hands and polish them into shiny round balls. I have done it with the clay bearing soils here in Tucson.
 

Gary Davis

Active member
Aug 29, 2022
29
Modesto, California
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
Use a skimmer sock in the skimmer with a skimmer vac plate and vacuum the dust.
That sounds like an idea I should explore although my skimmers don't work the way most do so using the skimmer may or may not be feasible.
My skimmers are not plumbed to the main drain filter pump and (I think as a result) they don't develop anywhere near the same suction.
The skimmers run on a separate popup pump which isn't filtered and you can barely feel any suction if you connect a 2-inch blue corrugated hose.

But I think there's a way, possibly, to run a vacuum from the main drain debris collection canister, but it doesn't have anything directly to do with the skimmers.
It develops a ton of vacuum but I'm always afraid of starving the pumps whenever I test it out so it's risky unless I know what I'm doing.
One test you can do on the dust is to put a drop of acid on the dust to see if it bubbles, which would indicate calcium carbonate.
Most likely, it’s calcium carbonate from the cement and the aggregate in the plaster if the aggregate is marble.
I think that's a great idea to see if the dry powder bubbles when a drop of acid is added.
Marble aggregate is a gritty type of hard sand.
This is a very fine powder. The photo doesn't do it justice in that you can't grab anything between your fingers.
You can put 0.5 grams of the dry dust into 1 liter of distilled water and the TA and CH should increase by 500 ppm if the substance is calcium carbonate and if all of the substance dissolves.
Now that's a GREAT IDEA! I like it. All I need now is to collect the fine powdery dust.
If only some dissolves, the levels will increase accordingly.
That is ANOTHER assay which pollen grains should fail, right?
Does pollen "dissolve" in water? Probably not.

But dust from the farms nearby might dissolve too, right?
Calcium hypochlorite will often leave this type of dust, so make sure that you don’t use calcium hypochlorite for a while before doing the test.
It has been years since I've added calcium as the water is a few years old.
Dissolving plaster will often cloud while brushing, so that can be a good indicator.
When brushing the sides, there is a small puff of dust but it's just stuck to the sides I think.
Some cleaners have fine mesh that will collect dust.
The pool doesn't have a vacuum port plumbed.
Do you have a cleaner other than the in-floor system?
Unfortunately not. The only filtering is done with the main drains. Even the skimmers are unfiltered (save for the baskets).
The cartridges will often collect plaster aggregate, so you can see if the cartridges have any aggregate in the pleats as you clean the cartridges.
That will probably work - but removing the cartridges is a lot of work compared to finding a way to just collect the dust and let it dry.
Maybe clean the cartridges over a fabric that can allow the water to pass through but fine enough to collect any aggregate dust.
The cartridges haven't been cleaned in a year so they will contain a lot of extraneous debris - but I could possibly clean the cartridges and then filter the dust only but that's a lot of work (those cartridges, when wet anyway, weigh something like a hundred pounds it seems). They're not small.
If the dust does not dissolve well in distilled water, try putting a drop of acid in the water to lower the pH to see if that makes the dust dissolve faster.
That's a great idea to put a drop of muriatic acid to see if it dissolves as I would think algae wouldn't dissolve, would it?
What about pollen?
Or clay?
Because we live in the Central Valley and it is the middle of almond harvest season? Dust is in the air.
When the wind blows, it gets so dusty you can grit your teeth in it, so it still could be a fine white clay dust.
Suction up a sample of the debris you are seeing and filter the solution through a coffee filter then let it dry.
Nice idea. I only drink powdered instant coffee but I can pick up a few of those white cupcake shaped filters at the grocery store.
I might even just drag a five-gallon bucket and collect enough water to filter through those coffee filters.
I like that idea! (It may not work because a five-gallon bucket is big and a coffee filter is small - but it might work!).
I like to use a 1/2" PVC pipe holding my thumb over the end until over the sample site, then transfer the contents into a container.
Oooh. Since I don't have any vacuum, that is a small hand-held one-shot vacuum pump.
Great idea!
A diving mask and a turkey baster works too but you may need some diving weights to counter boyancy if in the deep end.
I used to scuba dive so I have weights & a belt somewhere but I can hold my breath for a while on a mask & snorkel, as it's only 10 feet deep.
The turkey baster seems like the SIMPLEST idea. I'm no cook but I used one recently to suck out my power steering fluid so I have one in the garage.
Start by using a 10X loop or dissecting scope to look at it.
I used to have a loop. I can't find it. I do have a microscope though.
If you want to test it for calcium find a local ag lab and explore your test options.
Also you can run an OCLT with your test kit to diagnose algae.
I think your ideas for suctioning up the fine white powder will work and then I can run that test for algae.
I'm not sure yet if there is a pollen test - but maybe if all else fails - it's pollen. :)
Long ago I used my Dolphin robot cleaner with the ultra fine pleated filter to capture lots of fine silt.
These pools don't have vacuum lines plumbed but I like the idea of a coffee filter.
I rinsed the filter panel into a coffee filter and captured all the fine dust. I let it dry and it was the consistency of talcum powder. I live in the Sonoran desert … dust here comes mainly from fine clay particulates.
We have a lot of dust here also. You can grit your teeth with it sometimes but we also have a lot of pollen.
You can sift the soil here to remove the aggregates and sand and what’s left behind is moldable clay. The Japanese have an art form called durodango which literally means “mud dumpling” … you can mold clay bearing soils into spheres using your hands and polish them into shiny round balls. I have done it with the clay bearing soils here in Tucson.
The kids once took some of the soil out back and tried to make "baked clay" by wetting it thoroughly and then when they were done, they "baked it" by throwing it on a rock where it dried to a half globe in a few days. Then they baked it in the oven until the whole house stunk of a bog-like smell I've never smelled before (or since). Lastly, they "cooled it down" by dropping it into an open pail of varnish I was using on an outside door.

Wouldn't you know it, it cooled down to a rock-hard clump of home-made paleolithic clay that they brought to the science teacher for extra credit.
 
Last edited:

JamesW

TFP Expert
Mar 2, 2011
31,539
My skimmers are not plumbed to the main drain filter pump and (I think as a result) they don't develop anywhere near the same suction.
The skimmers run on a separate popup pump which isn't filtered and you can barely feel any suction if you connect a 2-inch blue corrugated hose.
The water should be filtered or the pop-ups will clog.

Check the screen to see if it is clogged.
main drain debris collection canister
Maybe put a skimmer sock in the canister and brush the dust to the main drain.
Even the skimmers are unfiltered (save for the baskets).
Why isn't there a filter?

Seems like a very inefficient design.
That will probably work - but removing the cartridges is a lot of work compared to finding a way to just collect the dust and let it dry.
It's not that hard and you you seem to think that it's important to get this dust for analysis.
The cartridges haven't been cleaned in a year so they will contain a lot of extraneous debris
Then it's definitely time to clean them.

Catch all of the debris and then get a mesh that is fine enough to catch the larger debris while allowing the dust to go through.

Can you show a picture of the pool and the system?
 
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JamesW

TFP Expert
Mar 2, 2011
31,539
That will probably work - but removing the cartridges is a lot of work compared to finding a way to just collect the dust and let it dry.
Do you have a lot of pool experience?

How long have you been at this house?

Did you have the pool installed or did you buy the house with the pool?

When was the plaster last redone?

Are comfortable in general with chemistry and working on equipment?

What are all of your current chemistry readings?

What plaster do you have?
 
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Gary Davis

Active member
Aug 29, 2022
29
Modesto, California
Pool Size
25000
Surface
Plaster
Chlorine
Liquid Chlorine
Turkey baster and white white paper towel in a strainer.
Indeed, that turkey baster worked like a charm when the results were put in a bucket and strained through my wife's nylons.
That way, this morning, I collected more dust than I need to the point that I could sell it if there was a good use for it. :)

It's all drying in the sun right now in a protected container.
However, I'm leaving for a long European vacation so I may not be able to run the assay right away.

Whatever we find out will be good for others who just want to run a direct assay of their pool dust.
 
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