Puzzled by Pool Stains-Baqaucil

jnmahone

Member
Mar 31, 2021
17
Central Texas
Possibly calcium carbonate with various other compounds mixed in.

Did you add any calcium chloride or sodium carbonate?

Try dissolving in distilled water and then test using a biguanide test.
James,
I used 12oz of distilled water and took an initial water reading:
ALK: 0
PH: 6.2 or less
BIGUANIDE: 0 ppm

I then put ~1.5tbsp of vacuumed scale into the water and stirred it around for about 5 mins. Subsequent water reading after stirring:
ALK: 40
PH: 6.5
BIGUANIDE: 0-2 ppm (color reading almost the same as pure distilled water)

Subsequent reading after letting sit idle for another 15mins:
ALK: 50
PH: 6.8
BIGUANIDE: 0-2 ppm

There seems to be some dissolving or breakdown into finer particles going on, albeit at a slow rate ... Not sure how much of that was a result of me stirring.

Interested in your thoughts ....
 
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JamesW

TFP Expert
Mar 2, 2011
24,112
Let the mixture sit for 24 hours and stir or shake occasionally to increase dissolution.

Then, test for biguanide, calcium, alkalinity and ph.
 

JamesW

TFP Expert
Mar 2, 2011
24,112
Based on the increase in alkalinity, I would suspect that the substance is mostly calcium carbonate.

If the calcium increases by the same amount as the alkalinity, then it is at least partly calcium carbonate.

I don't know why it would have made any scale based on the available information.

I suspect that the yellow is biguanide, but I don't know a lot about biguanide.
 

jnmahone

Member
Mar 31, 2021
17
Central Texas
Ok Thanks ...

I could be wrong, but I believe part of the yellowy olive color is actually algae. We had algae settle in initially and then the scaling seemed to happen over a few months.
Also for those ~4 months in the off season, we weren't checking PH. It was already borderline high @ 7.8 when we closed up so maybe it got higher and created the right conditions for calcium deposits. Just a theory as I try and learn as I go here.

I will post new mixture readings after 24hrs.

Given the fact that CLR, - which seems to be primarily gluconic and lactic acid, maybe small amounts of sulfamic acid and other ingredients, - seemed to eat away and dissolve the scale in experiments, are there recommendations of something similar but more concentrated for pools that are still safe for vinyl liners, potentially phosphate free etc ...? Maybe jacks copper and scale or bio guard or natural chemistry products ??
 
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JamesW

TFP Expert
Mar 2, 2011
24,112
Jack's copper stuff is sulfamic acid, which might work but it will lock up the chlorine for weeks or months.

Does the mixture have a calcium reading now?

Do you have a picture of the whole pool?

How much total scale is there?
 

jnmahone

Member
Mar 31, 2021
17
Central Texas
I do not have anything that measures just calcium but I measured total hardness and here are measurements of 4 water sources:

Distilled Water:
TH: 0
ALK: 0
PH: 6.2

Distilled Water w/ scale added (after 4ish hrs):
TH: 240
ALK: 80
PH: 7.0

Pool Water:
TH: 1000
ALK: 110
PH: 7.6

Well Water:
TH: > 1000
ALK: 200
PH: 8.0

NOTE: In all cases CYA, FC, and TC/TB are zero because we do not use chlorine for treatment.
There was mention that some of the scale remover products, lock up chlorine for awhile. Are there any effects when using H2O2 and biguanide as treatments instead of chlorine?
 

JamesW

TFP Expert
Mar 2, 2011
24,112
Ok. Thanks for the additional information.

Your CSI is very high and you definitely have calcium carbonate, magnesium carbonate and other scale with various other compounds mixed in.

It's a bad situation with no easy answers. It might not be a recoverable situation.

I really don't know much about biguanide.

So, take that into consideration before deciding what to do.

You could drain and refill if it's safe to do so, but that's not going to get rid of the scale.

You can try lowering the TA to zero, but it might ruin the liner or equipment and it might have a bad reaction with the biguanide. Extended low pH will ruin the liner. So, if you try the low pH, don't leave it for too long.

You can try sulfamic, but I don't know how that will react with the liner or biguanide.

Check with the maker of Jack's copper stuff to see if it's compatible with your chemical products.

I would probably try lowering the TA to zero to see if that works. If you have a heater or other equipment that contains metal, you have to make sure that the low pH water does not get to the equipment.

If the scale comes off, increase the TA back to about 60 with baking soda to bring the water back to a good pH.

If not, I would try sulfamic acid.

Just be fully informed that either method can potentially go horribly wrong.

Only you can decide if you want to take the risk.

Even if the scale comes off, the hardness is so high that scale will come right back unless you manage the CSI.

If you can get the scale off, you might want to drain and refill if it's safe to do so.

Don't drain and refill unless you are sure that you can do it safely.

Do at your own risk.

Do your own due diligence and research before deciding what to do.

You might end up needing to replace the liner or pool if you can't find a good solution.
 
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JamesW

TFP Expert
Mar 2, 2011
24,112
Check with the maker of your chemistry products to see if the low pH or sulfamic acid will be a problem.
 

jnmahone

Member
Mar 31, 2021
17
Central Texas
I guess one last question. Are there recommendations to control the CSI on simplistic pool like this, given our water is very hard and we probably don't want to truck in city water every time we need to replenish?
We could use softened water, but opted not to since the softening system would need to recharge often, not to mention go through lots of softener salt.
 

JamesW

TFP Expert
Mar 2, 2011
24,112
Are there recommendations to control the CSI on simplistic pool like this, given our water is very hard and we probably don't want to truck in city water every time we need to replenish?
The CSI can be managed, but you need to know the calcium hardness instead of the total hardness.

Once the calcium gets above 500 ppm, the CSI becomes increasingly difficult to manage.

Go to the PoolMath page to calculate your CSI try some different values to see what happens as you change the numbers.


 
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anthonypool89

Gold Supporter
Aug 26, 2016
645
Berks County, PA
I suspect that the yellow is biguanide, but I don't know a lot about biguanide.
I may be wrong but doubt that it'd be yellow since the titration for biguanide testing is in gradations of blue. At any rate, the liquid in the sanitizer / algistat containers is blue.

I've never had any sort of staining that I would say is specifically attributable to the use of biguanide. Your story, though, brings back a really bad memory in that when our pool was filled with mostly municipal water trucked in from a fire hydrant in town - it left a lovely brown ring on the brand new plaster at every place a water load ended. THEN the next day (or day after - can't recall) I got a letter (yeah...this was before the days of internet) from Anthony saying that I shouldn't forget to add "pool magnet" while the water is going in. ARRGGHH!!!! 'Too little, too late' as the saying goes. Those stains, while having become somewhat less obvious over the decades, were still there the day that the pool was drained and renovated. The other nightmare from that evening was that it had been raining pretty good and so the fire trucks that brought the water wound up digging up the lawn to the point that the entire thing had to be graded and reseeded. Horrible experience for a new pool owner. The driver finally told me that there was no way he could come around the lawn to do one more load for fear of getting stuck. Oh yeah..one of those nights I tried (unsuccessfully) to forget. Can still recall every detail 32 years later.
 
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