Passed SLAM tests, still seeing plaster stains

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Y

yardoasis

0
May 20, 2014
155
Houston, TX
Up until earlier this week, my pool wasn't holding chlorine. It was getting eaten up by organics and algae. SLAM'ed my pool for 4 days, and this morning I passed the 3 tests:

1. Water is glassy clear
2. OCLT < 0.5
3. CC = 0

Here's a full set of test results as of now:

FC: 16
CC: 0
CYA: 45
CH: 260
TA: 100
pH: 8.0

Just added 2 quarts of muriatic acid to lower that pH.

However, I'm still seeing those plaster stains. I want to say that the stains are getting better, but I'm afraid there's too little improvement for my liking.
Did the vitamin C tablet in a few spots, none has cleared up so I can rule out iron.

Based on my test results, what do you think it is? I really hope there's a way to get rid of those without having to drain and acid wash... I mean, I just got this pool built 2 months ago and the swimming season has just started. Maybe it's because of high pH and it'll go away when I lower it? Will borates help?

Couple of pics:

photo24.jpg


photo15.jpg
 
No borates won't help that... and you don't want to deal with borates at this time.

That looks like calcium scale to me - from high PH. Lower the PH to 7.2 and continue brushing. For the first year the PH, TA and CH will all change as the plaster cures. Brushing and keeping the PH in check are essential.
 
Thanks poolmom. Since your response, I've been keeping the pH low, in the 7.2-7.4 range and brushing the plaster. This is going to take time, right?

My CH is currently at 325, so maybe that has something to do with the scaling. That 260 reading in the first post was probably a mistake, I think I miscounted the number of drops by 2. :oops:

325 is still within the recommended range, but on the high side. Need I be concerned about a CH of 325, or is it just a matter of keeping the pH low enough?
 
Keep the ph down and try to set up a method to harvest rainwater. ... No ch in rainwater.

Do some playing with pool math and look at what various combinations to to the csi. Note the effect temperature has as well. You want to keep your csi down to help pull the scaling off of the plaster. It will take time and lots of brushing.
 
Well, we are all kinda' guessing it's calcium scale (and I agree with that) so it will take possibly the entire swim season to start reducing them (short of a drain and acid wash or a no-drain acid wash).

I think if it was my pool, I would get familiar with holding a low pH (7.0 - 7.2) and collecting rainwater to reduce your CH. Just controlling those two parameters may do the trick. What is the CH of your fill water?
 
The CH of my fill water is about 175 or so. Looking back, when I was being "pool-stored", I asked them for advice when the plaster stains first appeared, they sold me cal hypo shock and calcium hardness and told me to dump it into the pool.

No wonder my CH shot up to 325 :-| All the more reason not to trust pool store advice!!!

Last night I got about two inches of rain so that should shave a few points off my CH. For the next big rain, I'll look into harvesting rain water and search some threads about this.

I searched some threads about a no drain acid wash, and while that may be something I'll look into, I'm hesitant to do it during the swimming season. So, for now I will keep the pH on the low side starting Monday and keep brushing daily, and allow the pH to rise before the weekend for safer swimming, then lower the pH again on Monday, rinse and repeat. And when it rains, I'll try to collect some extra rain water, and put it into the pool.

If there is no improvement by autumn, then I'll plan on doing a no drain acid wash during the off season. Think this is a good plan?
 
New test results from today:

CYA: 45
CH: 300
TA: 70
FC: 7.5
CC: 0
pH: 7.2

Been keeping pH in the 7.2-7.5 range by adding MA, good enough for us to swim and enjoy the pool. I've been brushing the plaster every other day, still no improvement. It feels like an exercise in futility when I brush because nothing seems to come off.

Also, my TA has come down (as expected)... at 70, is it now too low or just right? When I plug these numbers into PoolMath, I get a CSI of -0.4. Supposedly it should be dissolving the scale, but nothing seems to come off...?

Am I just being impatient? :mrgreen:
 

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Richard320 said:
Very impatient.
Click to expand...

LOL, figured as much! It's just the stains REALLY bother me. I spent so much $$$$ on getting my pool built, and within 2 months the brand-new plaster got stained.

I'm not even sure it's calcium scale. Here's what I DID rule out:

1. Iron (vitamin C test, spot did not fade)
2. Algae (slammed it already, water cleared up but no improvement in stains)
3. Phosphates (phosfree added to water a month ago)

I did put a trichlor tablet, which is acidic, against the stain, and it lightened up. But I don't know if that proves anything. I'm still debating doing an acid wash in the middle of the season, and I'm torn.
 
Plug all your numbers into poolmath. Don't neglect the water temperature. Look at CSI. If it is positive, Calcium will drop out and scale, if it's negative, it will leech from the surface. Between -.6 and +.6 it's not very active.

If you fiddle with the targets you can see what you need to do to keep CSI towards the negative. You don't want to go below -.6 or you'll damage the plaster. But something like -.2 or -.3 should soften up the scale some. That's what I did to that wall in the thread I linked.
 
So I took some sandpaper (100 grit) and sanded a few spots on the plaster that appears grayish. My idea is to differentiate between calcium scaling (which should come off via sanding), and gray mottling (which would not come off because the gray stains go deeper into the plaster).

Strangely, immediately after sanding, I did not see a color change. But only after several hours in negative CSI water (pH ~ 7.2), the spots brightened noticeably (within green circles). Does this mean it was calcium scale and I did not sand all the way through, but exposed it to negative CSI water thus helping dissolve the rest of the scale?

Note there is no correlation between stains, colors, and texture. Some stains feel very smooth, some rough. Same for non-stained plaster. I also have brownish streaks and greenish stains that look like dripping paint... I will need to test those, too. I think I have 2 or even 3 different types of stains, which may hopefully be solved with sanding and/or acid washing.

Thoughts?

plaster.jpg
 
So I think what you have is scale with perhaps some organic staining imbedded in the scale, which is why sanding helped fade the appearance. I'm not sure what sanding long term will do to plaster surfaces... but I do think it's scale.
 
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