Unfilterable particulate in pool

[coldpoolcanada]

Hey TFP,

I wanted to share by journey with this strange particulate matter that had plagued my pool for a month, and questions on what this was, and how to prevent this in the future.
For context, I have had this pool for 4 years now. Aside from a few hiccups here and there, I never had any major issues like this.

So start of the season we open the pool like normal. SLAM etc, the pool is clear and looks great. A week or two later, we notice the water is a bit cloudy, a bit strange, so we dump chlorine into the pool and hope it clears up.
As soon as we put chlorine it gets very milky, and stays like this for days, even though the chlorine level had dropped.
After waiting a week and adding in clarifier, some participate settled to the bottom of the pool.
However, when vacuuming this (through my sand filter), the participate was mostly going right through and returning through the jets, back into the pool.
I took a sample in a glass, as shown in the attached photos. This isn't granular sand, its an extremely fine substance that doesn't even settle to the bottom of the pool. Instead it appears like a cloud of cotton candy or a spider web.
I had heard that sand gets worn after a few years, and this filter was at least 12 years old so I replaced that.
I tried vacuuming again, and the same thing happened, the particulate was being sent back into the pool through the return jets.
This time I figured the spider valve was worn, and indeed it was. I replaced this expecting everything to work, but once again the particulate was passing right through the filter, back into the pool.
Finally, I bought this expensive flocculant, set the valve to recirculate, and waited for everything to settle.

What I found was shocking, a thick layer of this very fine particulate (as shown in the attached photos). This was over an inch thick and the deepest parts of the pool. It was only after vacuuming to waste I got rid of this substance.

So my questions for TFP are:

1) What exactly is this mysterious substance? Why did it appear out of nowhere after 4 years and somehow bypass both the old and new sand filter?
2) Was this causing the relatively small amounts of chlorine to whiten the pool?
3) How do I prevent this in the future, without the use of flocculants and vacuuming to waste? I ordered some glass medium to add on top of the sand but I don't know if this is a valid solution.

Edit: I had dumped a large amount of solid chlorine, to the point that it was well over 10PPM (limit of test strip), would this still harbor algae?

 

[Texas Splash]

Good morning and welcome! The first place we would need to start is with a full set of water test results from your Taylor K-2006C. Or perhaps you have a TF-100 or TF Pro Series kit if you travel south to the US? But we need to see a full set of test results from one of those reliable kits first to be sure. I suspect you have algae. Everything you describe points to it, and when you have algae, no amount of filtering will resolve it. By the way, sand never gets worn or goes bad UNLESS someone adds floc or clarifiers to the water and it makes it to the sand. Something to keep in mind later.

You might want to star reviewing the SLAM Process page, but let's see what your test results show as well.

 

[sande005]

What product did you use when you added chlorine, and it got milky?

At a guess, I'd say something that contains calcium hypochlorite. That can cause the cloudiness by precipitating out calcium compounds, especially if pH and TA are not great (according to Mr. Google - I'm no chemist)
I had that issue a number of times, and did as you did - lots of clarifiers and floc. General advice says that by itself the chemical cloudiness goes away quickly, but mine did not - it could be a week or more with no change, before I started dumping stuff in the pool. And there may be dead algae floating around in the mix, compounding the cloudiness. My ultimate solution back then, stop using the powdered shock products, and only use liquid chlorine to "shock" the pool.

Clarifiers and floc will cause whatever is in the mix to clump, and you can get that deep carpet of "stuff" all over the bottom. So in that respect they work. It is only lightly held together, and disturbance (brushing/going through a filter) breaks them up and the cloudiness returns...and you then try more floc to fight it. So one must vacuum to waste to get it all out of the pool. Getting it all may mean a LOT of water being removed from the pool and needing replacement. And you may need to repeat a a day or a couple of days later a few more times, as residual keeps dropping stuff to the bottom. It can gum up your filter, necessitating a deep clean of the sand or even replacement of the sand. More here: Flocculant - Further Reading.

Start, as Texas Splash advised, and get yourself a K-2006C test kit. No other, unless you can get one of the others he specifically mentioned from the States.
NEVER trust strips or Pool Store results. They have proven to be wildly wrong.
Read the articles here under Pool School about recommended levels, the CYA to CL relationship, and the SLAM process (no one here recommends a one time "shock").
Go to your profile here, and in the signature line, add in the particulars of your pool (gallons, make/models of all equipment, test kit used, etc.) as others have done - keeps us from asking over and over about things you've answered.
Run all of the tests available in your kit, and report back here for advice.
Note what you are using currently to treat your pool - chlorine type, pH control, etc.
Download and use the PoolMath app. for easier calculation of how much of what to add.

 

[coldpoolcanada]

Good morning and welcome! The first place we would need to start is with a full set of water test results from your Taylor K-2006C. Or perhaps you have a TF-100 or TF Pro Series kit if you travel south to the US? But we need to see a full set of test results from one of those reliable kits first to be sure. I suspect you have algae. Everything you describe points to it, and when you have algae, no amount of filtering will resolve it. By the way, sand never gets worn or goes bad UNLESS someone adds floc or clarifiers to the water and it makes it to the sand. Something to keep in mind later.

You might want to star reviewing the SLAM Process page, but let's see what your test results show as well.

What product did you use when you added chlorine, and it got milky?

At a guess, I'd say something that contains calcium hypochlorite. That can cause the cloudiness by precipitating out calcium compounds, especially if pH and TA are not great (according to Mr. Google - I'm no chemist)
I had that issue a number of times, and did as you did - lots of clarifiers and floc. General advice says that by itself the chemical cloudiness goes away quickly, but mine did not - it could be a week or more with no change, before I started dumping stuff in the pool. And there may be dead algae floating around in the mix, compounding the cloudiness. My ultimate solution back then, stop using the powdered shock products, and only use liquid chlorine to "shock" the pool.

Clarifiers and floc will cause whatever is in the mix to clump, and you can get that deep carpet of "stuff" all over the bottom. So in that respect they work. It is only lightly held together, and disturbance (brushing/going through a filter) breaks them up and the cloudiness returns...and you then try more floc to fight it. So one must vacuum to waste to get it all out of the pool. Getting it all may mean a LOT of water being removed from the pool and needing replacement. And you may need to repeat a a day or a couple of days later a few more times, as residual keeps dropping stuff to the bottom. It can gum up your filter, necessitating a deep clean of the sand or even replacement of the sand. More here: Flocculant - Further Reading.

Start, as Texas Splash advised, and get yourself a K-2006C test kit. No other, unless you can get one of the others he specifically mentioned from the States.
NEVER trust strips or Pool Store results. They have proven to be wildly wrong.
Read the articles here under Pool School about recommended levels, the CYA to CL relationship, and the SLAM process (no one here recommends a one time "shock").
Go to your profile here, and in the signature line, add in the particulars of your pool (gallons, make/models of all equipment, test kit used, etc.) as others have done - keeps us from asking over and over about things you've answered.
Run all of the tests available in your kit, and report back here for advice.
Note what you are using currently to treat your pool - chlorine type, pH control, etc.
Download and use the PoolMath app. for easier calculation of how much of what to add.

Although I didn't follow the SLAM process, I dumped enough powdered chlorine into the pool that the test strip was reading above 10ppm for at least a day. The pool was also cold, ~20C at the time, so I don't understand where the algae would come from and how it would survive high chlorine conditions. I made sure the PH/ total alkalinity was good, and had no stabilizer.

What confuses me is whatever the particulate was, it would go right through the sand filter. This happened after shocking etc and the particulate was on the pool floor.

 

[Flying Tivo]

What confuses me is whatever the particulate was, it would go right through the sand filter. This happened after shocking etc and the particulate was on the pool floor.

Confusion comes from inaccurate information. I would suggest you start by reading Pool Care Basics, ordering the recommend
Test Kits Compared. Make sure you vacuum to waste that white precipitate matter. Dont do anything else until you get your test kit and have reliable information. You can add 5ppm of liquid chlorine daily to keep it from getting worst. We will be here to help you out and get you stared on a troublefree pool.

 

[sande005]

It all depends on what products, specifically, you have been using to put Cl into your pool. Let us know what they are. Just referring to "powder" doesn't give any information.

Test strips are notoriously very wrong. You simply must get the good test kit to accurately know what is going on with your pool.

If the powder contains Calcium Hypochlorite it caused the cloudiness due to a chemical reaction. The result is far too fine for the filter to capture.

20C is not near cold enough to deter algae. I've seen it when uncovering my pool in the spring, and the water temp is 10C or even less. Colder water just slows it, but it still grows.
You may have had that too, which provoked you into adding the "powder". Sand filters, sometimes, can struggle to trap all the dead algae - a lot depends on the specific equipment (filter, pump, how it is operated, etc).

Per your first post - a SLAM is not a one time dumping in of extra Cl. It is a process, usually over several days, that has a very specific end test to verify that you are done.