Sandpaper-like grit (calcium crystals?) suddenly on entire pool surface, polaris and hose...

james0125

Member
Aug 17, 2019
13
Austin Texas
We have an in-ground pool with the following specifications

  • Location: Texas
  • Recent water Temp over past ~month: 85-90
  • Pool Age: 3 years
  • Size: ~15,000 gallons
  • Water Type: Chlorine
  • Pool Finish: Wet Edge Primera Stone
    • * This is a more unique finish. It is an plaster-stone aggregate (similar to Pebbletec), with a major distinction. After the aggregate is put in and dried, it is hand-sanded/polished to have an end result of a marble-like smooth finish.
Todays Readings
  • Free Available Chlorine: 0
  • Total Available Chlorine: 0
  • pH: 8.0
  • Total Alkalinity: 180
  • Cyanuric Acid: 99
  • Calcium Hardness: 420
  • Total Dissolved Solids: 1100
  • Copper/Iron: 0/0
  • Phosphates: 300

We swam in the pool 2 weeks ago and it was fine.
Between that time and now, the water has 'looked good' and I've been maintaining CL and pH.

** We stepped in last night however, and the "entire surface" of the finish has a sandpaper-like grit feel.... It's even on the Polaris and the cleaner hose.

In a small area of the wall I used a plastic putty knife and the grit comes loose. A pumice stone works really well, but we went through 3 stones just attempting to remove the grit from the 1st large step/sun deck. I tried the standard pool brush, both nylon and wire, but it does not remove the grit.

To Reiterate:
  • Plastic Putty Knife: works OK.
  • Metal Putty Knife: works very well and removes the grit
  • Pumice Stone: works very well, just eats up the stone quick
  • Standard Nylon Pool brush: does not work
  • Stainless Wire Pool Brush: does not work

So, given the fact that it can be scraped off, my understanding is that its not calcium scale but perhaps calcium crystals? In my research however, it seems that this is more common in colder climates and especially present on pool openings. Given this, its especially confusing because my climate is 100+ degree days and the pool has been open for 3 months now with no issues.

I'd really would like some community feedback here.
I went to our local pool supply store, but I'm not entirely confident in them or their recommendation. They recommended, which I purchased, but have not yet used: Stain & Scale Remove which indicates 'Highly concentrated calcium and metal stain remover'.

Thanks again. Hope to hear some feedback soon.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Welcome to TFP! :wave: Based on your test results and description, you may be seeing the signs of scale. You can confirm by collecting some of that stuff scraped off, place in a pile, and pour some acid on it. If it fizzes, it's calcium scale.

Your numbers need help....IF they are accurate, but I suspect those are pool store tests right? If so, stop. You really need to test your own water with a TF-100 test kit (or Taylor K-2006C). That is #1. Also look at our PoolMath tool. Enter all those numbers and look at the "CSI" row. Your CSI must be extremely positive (high) with a high potential for scale.

I would do the following right away...
1 - Order a TF-100 right away and avoid pool store tests and gimmicks. Those over-priced solutions won't help.
2 - Get that FC up immediately with regular bleach/pool chlorine (same thing) ASAP. Raise the FC to at least 6-8 for now to avoid algae. See FC/CYA Chart
3 - Then lower the pH with muriatic acid. You can get the chlorine and MA from Home Depot. Lower the pH to the lower 7s for now. It's safe because your TA and CH are already elevated, so a pH of about 7.2-7.4 is fine. Start brushing a lot to help break-up that scale.
4 - If you are using tabs/pucks - stop.

Once you get your test kit, post a full set of new numbers. A healthy water exchange may be in order to lower your already elevated CYA (from pool store products). Stick around, we'll help.
 
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james0125

Member
Aug 17, 2019
13
Austin Texas
Thanks for the quick reply!
I see you are in SA TX.... We are right down the road in Buda.

Those tests listed above were indeed run by the pool store this morning...

Today I did the following:
  1. Got test results from local pool store
  2. Scrubbed what I could with the pumice stone
  3. Pump was on high to aid in collecting grid scrapped off
  4. Polaris was running to collect as well
  5. Added 1 qt of acid to attempt to lower pH from stores reported 8.0
  6. Posted this post...
  7. Got your response...
  8. I pulled the Polaris and dumped the content.
    1. I added acid on the gritty content, and indeed it fizzed/bubbled.
    2. I also poured some acid on the Polaris. I mentioned before even it and its hose felt like sandpaper. Doing this, the grit immediately bubbled away and left the plastic buttery smooth again.
  9. I do have a Taylor 2006C, so I ran some tests with the following results
    • TA: 260
      • store reported 180
    • CH: 500
      • store reported 420
    • pH: ~8.0
      • store reported 8.0
    • FAC/TAC: 0
      • still need to add

* Regarding your #4 step comment stating
If you are using tabs/pucks - stop.
Tabs/pucks of what? 3" Chlorine tabs? My standard practice is to use 4 of these a week. I usually add the 4 tabs every Friday, but its been about 1.5 weeks now which is why the Chlorine level is 0.
After any pool parties, I then administer 1 gallon of liquid shock. This combination of 4 tabs a week and shock after lots of activity has always done the trick for the past few years.

I administer the 3" Chlorine Tabs via a "Nature2 Fusion Chlorine Tablet Feeder + Nature2 System"
Nature2 Fusion Inground

I also sanitize with an Del Ozone Eclipse 10
Del Ozone Eclipse 10
 
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Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
14,639
Bedford, TX
James,

Just for reference, we tell everyone to maintain their CSI between +.3 and -.3 Using your numbers, your pool is running at a +1.14.. Just slightly out of spec. :confused:

I suggest that you read through pool school and see why we do not recommend mineral systems such as the Nature 2 and/or Ozone systems...

I suggest you start here... ABCs of Pool Water Chemistry

If you decide you are interested in following the TFP pool care process, just let us know..

Thanks,

Jim R.
 
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james0125

Member
Aug 17, 2019
13
Austin Texas
I've using the PoolMath calculator, have entered the following, and have some questions.

  • Suggested Goal Levels
    • Traditonal Pool
    • Trichlor chrlorine tabs
    • Plaster
  • Size: 15,000
  • Temp: 90
  • FC
    • Now: 0
    • Goal: 7-8?
  • pH
    • Now: 8
    • Goal: 7
  • TA
    • Now: 260
    • Goal: 100
  • CH
    • Now: 500
    • Goal: 350
  • CYA
    • Now: 99
    • Goal: 50

It's calculating my CSI as 1.15 with a goal of -0.38.

Are all my goal numbers correct?
The recommended FC of 7-8 seems really high. Was that a typo Texas Splash?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,798
Northern NJ
Reasonable goals for your pool are :

FC - 8
ph - 7.6
TA - 80
CH - 250
CYA - 50
CSI - -0.20

To achieve this you need to replace 50% of your water that will lower your CYA and CH.

After you do that you need to lower your TA. See ...


What is the pH and TA if your fill water? You have an autofill on your pool?
 
Texas Splash is the expert, so I’ll let him guide you through your numbers. I’ll say for now, though, that the chlorine guidance was not a typo. It’s based on the science of how CYA binds to chlorine. We need that CYA with all our Texas sun, but we have to run seemingly high chlorine levels for it. The traditional recommendations for chlorine between 1 and 4 are for pools with no or very limited stabilizer.

Our family moved to Texas in 2017 and bought a house with a pretty old inground pool. The previous owners left behind some empty buckets that showed that they chlorinated with trichlor pucks and cal-hypo shock. The pool wasn’t wretched, but it had a lot of calcium scale, and what made it worse was that there was algae staining embedded in the scale. It made it look as though the pool had algae even when I had eradicated it with TFP’s SLAM process. Following the science here about how to chlorinate (I had to use liquid because my CYA was already high) and how to keep my CSI negative (for me it meant adding a good amount of MA every time my pH rose even to 7.7), all the scale dissolved over the course of our first spring and summer with the pool, and I have pretty smooth white plaster again.

I just thought it might encourage you to hear that your beautiful finish is recoverable, and it isn’t really even too hard. Chlorinating liquid and muriatic acid will be your best aids.
 
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Let me also add that I did this without draining my pool substantially. We have a community well and had pretty strict water restrictions. We had CH of about 575 and CYA around 90. Last fall’s torrential rains helped us mightily by replacing pool water for us, so our calcium is 300 now, and we try to fill with stored rainwater to help keep it down. It’s easier to manage CSI when all your numbers are in range, but people in the Southwest with high calcium and high alkalinity fill water can still manage it when those numbers aren’t ideal. Mostly it takes keeping the pH lower, but don’t shoot for lower than 7.2.
 

james0125

Member
Aug 17, 2019
13
Austin Texas
Thanks for all the advice so far. I certainly would like this channel of communication open as I try to get this under control.

I purchased shock today and added 1 gallon slowly over 2 minutes in front of 2 of my return jets.

Reading more it seems regular bleach is better? Should I grab some bleach and use that instead from now on rather than “shock chlorination”?
 
I think in the early days of TFP grocery store bleach was just economical. These days with changes manufacturers are making to the ingredients or concentration of bleach, pool chlorinating liquid is a better buy. It is often called “shock”. TFP also doesn’t like that term because of its use as a one time high-dose of chlorine, but liquid shock chlorination is just what you want for your pool. You should be able to get a case of three at Home Depot, and the price goes down if you get four cases of three. Just watch the dates: YYDDD. The first two should be 19, and the last three will tell you the number of days into the year it was made. You’d want to be in late one hundreds or into the two hundreds to make sure it’s fresh. It’s good to store it in a laundry room or pantry if you can to keep the heat from degrading it.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,798
Northern NJ
Liquid pool shock is a high cost source of liquid chlorine. You can find 10% chlorine at some Walmarts, Home Depot, and local stores. Or 6% plain bleach - no scents, not splashless, not Clorox.

There are threads here on where folks find their liquid chlorine. Like...


Use PoolMath to calculate the quantity required.
 
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james0125

Member
Aug 17, 2019
13
Austin Texas
Great advice.

A few more questions.
1. Do I want to get the chlorine up to 7-8 while trying to get the pH down with MA or should I get chlorine up then work on the pH?
2. Should I use my new stainless wire pool brush or stick with the standard nylon brush to brush pool plaster while I’m trying to get the scale off?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,798
Northern NJ
You can adjust FC and pH 15 minutes apart. Work on both of them.

I think wire pool brush will make more progress on scale than nylon brush.
 
I used the Old Poolmath page link at the bottom of the page and plugged in your pool specs listed above. With your high TA, I got that it would take 101 oz of muriatic acid to lower your pH from 8 to 7.2. That is assuming that your 15,000 gallons is correct. I’d be inclined to add less than the full amount, circulate the water for an hour, then test again. Sometimes you’ll find that you need to adjust your pool volume.

Important note: when you are calculating a pH change, you must put in a current TA so that poolmath can do the calculation correctly. Also, even though you may have a goal of getting your calcium to 300, if it’s still 500, you need to leave the 500 in the goal column in order to get an accurate CSI. The same applies to other levels like TA and CYA. When I plugged in your numbers this morning, even lowering your pH to 7.2, your CSI was still positive. It’s that super high TA of yours. I understand as ours is 290 out of the tap.

Allen put in the link above about lowering your TA. Read and ask questions to make sure you understand the process. With your high TA and existing scale, it would be well worth your time to focus on that.

About MA: you can buy that in a 2-pack at Home Depot as well. I believe the discount kicks in at two 2-packs. You just don’t want to store it near your chlorine or metal. Heat will not degrade it, so outside is fine.
 

james0125

Member
Aug 17, 2019
13
Austin Texas
I found out where I got my information. It’s in the manual/guide that came with my pool. It says

“DO NOT make rapid changes in the pH or TA or you may cause metals and minerals to precipitate and cause staining and scaling. You should gradually adjust the readings, adding no more than 1 qt of muraitic acid per 10,000 gallons per application”
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,798
Northern NJ
I got that it would take 101 oz of muriatic acid to lower your pH from 8 to 7.2
Note that PoolMath is not very accurate calculating pH changes of more than 0.2. So in making a big pH change do two or three doses 15 minutes apart testing in between.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,798
Northern NJ
I found out where I got my information. It’s in the manual/guide that came with my pool. It says

“DO NOT make rapid changes in the pH or TA or you may cause metals and minerals to precipitate and cause staining and scaling. You should gradually adjust the readings, adding no more than 1 qt of muraitic acid per 10,000 gallons per application”
There is a bit of truth to that. “Gradually” is 15 to 30 minutes between doses and testing. A day is unnecessary.
 
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Divin Dave

TFP Expert
LifeTime Supporter
Oct 2, 2013
5,631
Longview, Texas
Hi James,
Welcome to TFP.
For help with your pool chemistry, you've certainly come to the right place.
As is evidenced by the pool store recommendation to add scale remover, they are only looking at removing the symptom, and not the fundamental issue of why it happened to begin with.

Our goal at TFP is to address these fundamental issues and help pool owners with the tools and knowledge to be able to properly maintain our pools ourselves.

The others are spot on in recommendations to your dilemma of CH crystals/ scale in your pool.

In review of your test results, you also have another fundamental water chemistry problem that if not address rather soon, will give you at least as much grief, if not more, than the CH scale.

I do not want to derail your current conversation, so continue with that in the short term, and then address your CYA.

The pool store reports your CYA at 99. We would like to see a titration test with your Taylor test kit (because we do not trust pool store computer testing). CYA buffers the effectiveness of Chlorine. For chlorine to be effective, the FC must be between 7.5% and 11.5% of whatever your CYA is.

CYA testing only measures the test up to 100ppm. Since you are already there, your CYA may well be higher than that. A diluted water sample of 50% pool water and 50% tap water should give you a somewhat accurate reading of what the CYA really is.

Its very difficult, and cost more money in chlorine to maintain a proper FC/CYA ratio, so lowering the CYA is the best course of action.

Unfortunately, there isn't a magic cure for high CYA. The only way to effectively lower it, is by dilution. To put it bluntly, drain some portion of the pool water and refill. To know how much to drain, you'll need to know what the actual CYA level truly is. So that's why the recommendation to test it with your taylor kit, diluted 50/50.

On the bright side, though, depending on what the CH and TA of your tap water is, a partial drain and refill may very well lower your CH, and help with controlling possibility of CH scaling.
 
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