Chemical oddity - Stabalizer

[WmRickert]

First of all I'd like to say thank you to everyone here.

I've been lurking for 2 years now and consider myself an armature chemist as a result.

This is my 3rd time opening a pool.

33' round (16.5 diameter)
4' sides
4.5' center
Estimated 28,000 gallons
However it historically reacts like it is 35000 gallons.

That said, this year I started without a cover and had to rake and scrub.

I started with a 0 FC a few days ago with a half full pool and CYA at 15.

I've been keeping the FC around 10-15 to kill algae. Once it did drop to 2 overnight.

So I keep testing every 3 hours - backwashing every hour or so at this point. (5 lbs of DE on top of a sand filter)

Here is the oddity.
The last time I scrubbed my CYA test shot up to over 100.
I did add a 4 tab floater of 90% trichlor tabs to slowly raise my CYA but that shouldn't account for the high reading.

Is there something about sustained shocking that will cause false readings?
PH was at 7.2 when I started, it has been around 7.8 while shocking and that hasn't changed.
TA has stayed consistent at 100 throughout.

I'll keep up with the persistence and patience.

Thanks again,
Bill

 

[Richard320]

Welcome!

If you water is really cloudy, that could skew things. Why not try a CYA reading without using any of the reagent, just check the turbidity (ain't that a fancy word for cloudy ) of plain pool water and see what it says.

 

[chem geek]

Welcome to TFP!

If you initially tested before having the circulation pump on for a while, you could have measured mostly rain water closer to the water's surface. Once the entire pool water got mixed, then you were measuring the true average CYA in the water. On the other hand, I would have expected your TA to change as well though rain water does have some TA (depends on its pH where it has higher TA at higher pH). It's more likely to be what Richard said. Not just basic turbidity of the water, but particles in the water can cloud up during the test more, possibly interlinking the melamine cyanurate precipitate with other particulate matter.

 

[WmRickert]

(I'll highlight the questions for easier reading.)

What is confusing is I ran a low CYA ~20 all year last year adding a little bleach each day.
I didn't want to raise my CYA any higher because I run about a 50-60ppm on the borates to reduce chlorine demand. (and the sparkling color)
20ppm CYA + ~50ppm borates cut cloudiness, stabilized chlorine demand and fixed the algae issues I had the year before.
Now after draining my pool 1/2 way before closing I opened it up to a 20, filled it the other half with tap water and got 100 which is way too high to sustain a 33' round pool on a tight budget.
Chlorine/CYA chart puts my chlorine levels at:
100ppm CYA
7ppm Minimum FC
12ppm Target FC
39ppm Shock FC

So, I'll try to decipher what you guys are trying to tell me.
The particulate in the water is causing false high readings. Correct?

What you are saying is that I should test the turbidity/cloudiness of the water without reagent.
This is not something I know how to do.

I am hoping that it is a false reading.
There is just nothing I know of that would raise my CYA 80 points over winter.
It would be great if I knew for sure that there wasn't anything that can happen without human intervention to raise my CYA so high.
Is there anything in leaves or algae that can raise the CYA?

Anyway, thanks again.
I'll continue to shock to 15ppm FC daily till it holds longer than just over night. It seems to be working

I started Saturday with a green swamp.
Algae is all dead and I'm only back washing 4 times per vacuum now even with the DE on top of the sand.
Water is no longer milky, only cloudy, and I can see the bottom.

Worst case scenario, just to confirm, draining a portion of my pool is the only way to lower CYA right?

 

[jcowart]

I think it is a test error due to cloudy water. As the other have said, run the test without the regent. Just don't add the R 0013.
My question is about the DE you add to your filter. You said 5lbs. Is that what it takes to raise the clean psi by 1. It was several years ago when I had a sand filter but it only took about a half a cup by volume.

 

[duraleigh]

CYA can only increase if you put some in there. If your CYA was 15 and you didn't add any, your CYA is still 15 ppm regardless of any test.

5 lbs of DE makes no sense....that is w-a-a-ay too much. Follow the SLAM article in the How To section of Pool School. I would add NO DE.

 

[Bama Rambler]

...What you are saying is that I should test the turbidity/cloudiness of the water without reagent.
This is not something I know how to do....

All you need to do is pour some water straight from the pool in the CYA view tube and see if it reads anything. If it does then the cloudiness is causing a false reading. however, I don't ever remember a case of that happening.

How are you testing the CYA?

 

[WmRickert]

{snip}

5 lbs of DE makes no sense....that is w-a-a-ay too much.

{/snip}
Correct. It was a 5lb bag. I added approximately 1/4 of that.
The procedure was to start with a backwash and clean basket at the pump.
I got my pressure reading at 8psi.
Tested for channeling with a handful of DE.
No blowout so I added till I brought the pressure up to about 11.5.
I was shooting for 10psi but ended up at 11.5.
No worries though. It will backwash eventually.

In fact today I'm at 10.5 after backwash.
I vacuumed and it was around 16psi before that.

I can go to 18lbs before I need to backwash based on water flow.

I know people who run dirty sand at 12psi.

Please correct me if I need to backwash it out.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Sorry for the absence.
I gave it a couple days to clear.
The DE caught everything floating and the rest of the dead algae settled. I scrubbed the sides the last 2 days and vacuumed both days as well.
Today I fished out the last 2 leaves.

I tested the CYA waist high with my back to the sun this afternoon. I got off early since I had some overtime earlier this week.
Finally got a good reading with all the turbidity cleared up.
CYA was at a 7. Just a bit lower than I figured it would be and should be easily fixed with some trichlor tabs.

TA was at a 0 so I added 12 lbs of baking soda.

I'll add 12 more tomorrow then another 8 Monday.

Or can I just add 20 lbs tomorrow?

CC is 0.

FC is steady at 4.75. I'm sure that will fall nice by tomorrow afternoon.

FYI my sides are 52" not 48" so the estimated 28000 is pretty close.
I didn't know it when we bought the house a couple years ago but I found out this is a pretty big pool.

PH is 7.6 when FC is at 5 so it should be well enough. I think.

I have 4x 8oz 90% trichlor tabs floating to bring up the CYA.
I'm not sure how many of those I'll need to bring it up to 20.
{snip}

In 13,000 gallons, 10 lbs of trichlor will raise the CYA level by 50.

{/snip}
I'm guessing a total of 24 tabs should do it.
Bringing my CYA up to around 20 in the next 6 weeks.
Is that correct?

Copper 0
Nitrates 0
Iron 0

Borates are at 12.
Goal is ~50

All around I think I'm pretty clean and just need to bring my TA up before I nail it with borox.
16x boxes of borox.
5x gallons of muratic acid.

I think that is correct.

Thanks for checking my math.

Last question.
Can I add borates the same day I bring up my TA with baking soda or do I need to wait a few hours or a full day?

Thanks again for easing my worries about the CYA.
I'm still a pup.

Oh and thanks for the patience too.
I'm sure my questions seem fairly elementary to you guys.