Scale Removal Help?

[dcaranci]

Hi,

First off, I apologize if I'm posting this in the wrong forum.... please let me know if I did and I'll happily move it. This one sounded like the most appropriate to me?

Does anyone have any suggestions about how to remove white scale from my pool liner?
Before jumping to "lower the water and scrub with xyz..." the scale I'm talking about is on the bottom of the pool so it's not possible to "lower and scrub".

For reference:
- Pool is a vinyl liner, in-ground, about 60,000L (25,000 gal), 8ft deep end about 3-6" shallow end
- I keep the water temperature between 78-84degF
- I'm meticulous about water balance (hardness = 220-250, alkalinity = 100-110, pH = 7.4-7.8, CYA = 40) as measured with a Taylor K2006 kit weekly
- It's a salt-water pool, salt level is about 3200 (what the Jandy SWG reports)
- No metals that I've seen on test results from the pool store (I can't test for metals)

I've had the kit and been keeping the balance well monitored for about 3 years now.

I'm not sure how this scale formed, pool is about 5 years old and I noticed this scale at the beginning of last year just after I converted to SWG. Doesn't seem to have gotten worse since then but it's not getting better either.

I do use BioGuard Stain/Scale Prevent, though doesn't seem to do much (750ml per month). That and a bit of blue clarifier and Banish algaecide (100mL of each weekly) is all I add to the pool regularly besides balancing chemicals. To keep things balanced, I use Muriatic Acid to lower the pH (about 500mL/week), cheapest Alkalinity booster I can find, and Balance Pack 300 to boost calcium when I need to though this year the alkalinity and hardness seem to be very stable so haven't had to add much at all of those since I opened it in the spring.

I've attached a few pictures to show what I'm talking about. It's really apparent around the seams of the liner, for some reason the scale doesn't form on the seams. Some spots are worse than others, like at the bottom of the stairs. Brushing doesn't seem to do anything.

Is there anything I can add to the water to dissolve this? Being a vinyl pool, I can't lower the water enough to scrub it with muriatic acid or any other cleaner so I "think" the only way to get rid of it would be to add something to the water to dissolve it?

Any thoughts/opinions/input very much welcome!

Thanks...
DoC

 

[Richard320]

Thoughts, you say?

Well, the first thing was "Why does he add Calcium to a vinyl pool?" Second was algaecide and clarfier.

I just plugged your numbers in and you shouldn't be forming scale. In fact, when the pH is low you'd be loosening it. So I wonder if it really is scale. Scale feels like sandpaper, literally. Like scuff your skin against it and get road rash. Or buff off your callouses and get a pedicure in the pool. Does it feel that way? If not, maybe it's the liner getting worn. If it does, then manipulate your numbers. Lower TA. Raise CYA. Run pH at the low end of safe. Don't add any more Calcium if you lose any water to splashout or rain. Do whatever it takes to get the CSI negative. You can go real low, since you don't have to plaster to erode. It should soften things. Be aware that it will happen at a glacial pace.

 

[dcaranci]

Thanks Richard for the comments.

I'm pretty sure it's scale... or something ON the liner. It's on the walls too, and there when I lower the water a few inches it can be removed with some acid pretty easily. It's not building that I can tell, it's the same as it was last year. It's just not going away. It's not all that rough but definitely feel a difference on the liner above and below the waterline, chalky feeling below. Funny thing I also noticed, if I let the water level drop 3-4 inches and expose the white on the liner, the sun seems to remove it after a few days of direct sunlight. I found that weird... definitely sun because it doesn't disappear on the shady side of the pool, just where the sun hits it directly.

I'll try running the CSI negative for the rest of the summer and see how it goes. How negative is "safe"? I generally try to keep it between -.5 to +.5. Not sure how low to bring it before any other bad things might start to happen (corrode?). Same question for pH... is 7.0 too low to be safe? Where should I target?

BTW, I add only enough calcium to keep it between 200-300 on the hardness scale and generally lower than 220 if I can. From this forum, I thought that was where it should be? As for the algaecide and clarifier, just add that as a backup/insurance measure... not much, just about 100mL per week.

Thanks for your input in advance!!!!

Cheers...
DoC

 

[Richard320]

You need to keep pH in the safe zone for swimmers, 7.2>8.0. Don't go any lower than that. Don't let the TA go below 50, or the pH will get unstable. Beyond that you can let CSI go as negative as you want.