Removing calcium scale on vinyl liner

Rangeball

Well-known member
May 25, 2007
785
Our fill water is high alkalinity, so I'm constantly fighting high PH due to drift. Due to a long illness with my mother in law last year, I wasn't able to keep on top of the the PH and it ran pretty high for the majority of the season. I now have calcium scale on a large portion of the liner.

When I closed the pool last year I adjusted the PH to 7.0 but the alk was still 150+. I had hoped the lowish PH would bring the calcium back into solution, and I think it did as it's not quite as bad as before, but it's still there.

I googled and found some older posts by Ben that talk of Sand algae and it seems like his recommendation was to lower PH to 6.8 and let it rise on it's own. I now have my alk at 80 ppm, so I'm hesitant in taking it that low as I have no idea how doing so will affect alk and what to expect.

When lowering Alk I drop PH right before a good rain, as I've found rain to be the best aerator going. When I've dropped PH and it doesn't rain like expected, it only takes a week at most for the PH to climb back up with no change in Alk. But that was at higher Alk levels.

Is this the answer? I assume I'd just use muriatic acid as before, but noticed that stain and scale products also lower PH quite a bit but have no idea if they'd be a better choice in this situation. Any help is greatly appreciated.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
The lowering PH approach can eventually get the scale off, but it can take a very long time. Plus if the CH level gets too high, which it will eventually, it will stop working until you replace water to get CH back down. Also it is important to not lower PH below 6.8 as that will damage the liner.

If the scaling is especially bad, most people end up replacing the liner.

In some cases it is possible to physically remove the scale and dispose of it. The challenge is to do this without damaging the liner.
 

Rangeball

Well-known member
May 25, 2007
785
The lowering PH approach can eventually get the scale off, but it can take a very long time. Plus if the CH level gets too high, which it will eventually, it will stop working until you replace water to get CH back down. Also it is important to not lower PH below 6.8 as that will damage the liner.

If the scaling is especially bad, most people end up replacing the liner.

In some cases it is possible to physically remove the scale and dispose of it. The challenge is to do this without damaging the liner.

I'm in no hurry and have nothing but time. Most people don't even notice, or at least no one has commented. I think it's because the scale is mostly in the deep end where they aren't touching. It's an older IG pool with only one return, so circulation isn't optimum.

I don't use any calcium based products. At what level of CH would you expect the scale to stop dissolving? It was all in suspension before, so I'm hoping it will return now that I'm being more diligent about PH.

If I drop the PH to 6.8 at 80 Alk, am I risking PH dropping lower due to instability from low Alk?
 

Go_Habs_Go

Active member
Jul 6, 2015
40
Montreal/Quebec/Canada
Just bumping an older thread to see if there was any update on this? I think I may have calcium scaling as well in my vinyl lined pool. I've had high CH and high PH this summer and now I seem to have this whitish-greyish sheen over part of the liner.

Rangeball: how did things work out for your pool??
 

Rangeball

Well-known member
May 25, 2007
785
I ended up closing my pool last season with the TA at 80 and the PH at 6.8. The scale was better this year when I opened, but still present. To date this has been a terrible season with all the rain, so I'm just now getting around to looking at this again. Still trying to determine if just getting the PH low and letting it slowly rise and keep brushing is the better choice than using one of the stain and scale products, which seem to just be different types of acid.
 

Rangeball

Well-known member
May 25, 2007
785
After all the rains my TA has dropped to 50ppm. PH is holding steady at 7.2. I'm contemplating dropping it to 6.8 and spending a lot of time brushing to see if I can get the rest of the scale to release/dissolve, but am wondering how what affect doing so will have on my TA and how long I can hold 6.8 without damaging my vinyl liner.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
If you don't have borates in the water, then lowering the pH from 7.2 to 6.8 by adding acid would lower the TA by another 8 ppm.

A pH of 6.8 over days is not a problem. You don't want low pH over months, but even 6.8 isn't very low for vinyl.
 

Rangeball

Well-known member
May 25, 2007
785
Perfect, that's what I wanted to hear.

I think I'll adjust my TA up to 80 to give me more of a buffer then drop PH to 6.8. We aren't supposed to get any more rain for a few days, but if we do this will give me some room without crashing TA if it does. Rain is a great aerator.

Thanks.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
I wouldn't bother raising the TA. It's high enough and having it lower will only help dissolve the calcium carbonate a little faster. Also the pH will want to rise from carbon dioxide outgassing and the lower TA will have a little less of that.
 

Rangeball

Well-known member
May 25, 2007
785
Ok. I'm probably just gun shy from dealing with my dad's 0 TA pool the past week. Didn't want it to crash.

Any guesstimate how long I should have to leave the PH low to get it dissolved? I plan to brush the heck out of it over the next several days, as much as possible. I did notice last night that it seems to be loosening up, I can now get it to wipe off with vigorous scrubbing.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,375
Tucson, AZ
What about trying something like this - Purity Pool OS Out Spot Stain Remover

The PVC container would allow you to add some diluted acid to it and the sponge on the end holds it in over the spot you are cleaning. It would give you some concentrated acidity right over your calcium spots. Seems easier than trying to drop the entire pool's pH and then waiting while the calcium slowly dissolves.
 

Rangeball

Well-known member
May 25, 2007
785
Interesting, thanks. However the scale covers probably 60% of my liner, that would take a lot of time. Plus, PH already dropped :)
 

Go_Habs_Go

Active member
Jul 6, 2015
40
Montreal/Quebec/Canada
Thanks for the update Rangeball! Hope that your scale clears up soon. I've dropped my pH down to 7.2 and that has helped as I am able to brush the whitish/greyish scale of my walls now. But some of it is still staying on, need to brush more! My aching arms and back...
 

Swampwoman

TFP Expert
LifeTime Supporter
Apr 27, 2012
3,835
Grand Rapids, MI
I have one of those spot removers Joyful nose posted about...the surface is kinda lie a gentle pit scrubber...you could try to scrub with that, though the MA will dissipate about every 15 min.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,375
Tucson, AZ
I have one of those spot removers Joyful nose posted about...the surface is kinda lie a gentle pit scrubber...you could try to scrub with that, though the MA will dissipate about every 15 min.
I wonder if packing it with solid acid (pH minus) would work better?

I wonder if this Jandy Stain Remover would work better as it allows you to hook it up to a gallon bottle of acid.


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