Pool mottling 4 years after re-plaster

[RANDY M]

Hi all,
Pool re-plastered in April of 2018. The mottling seems to have taken over in the last month. Is this something that can happen 4 years after re-plaster?
I did add 55 lbs. of boric acid 6 weeks ago to try to slow down the pH rise (that’s another post to come)
Also some of what I think are calcium nodules started appearing a couple months ago.
Does anyone know if this will eventually cover all the plaster? It wouldn’t be such an eye sore then.

FC – 5
pH – 7.8
TA – 65
CH – 650
CYA – 45
SALT – 2200
Borate – 38
CSI - .13

Thanks

 

[YippeeSkippy]

Hmmmm...I can't say I've ever heard of plaster mottling 4 years later, Randy?

Usual suspects are poor water chemistry and pouring chemicals on to the pool surface and not brushing them in/around to dissolve into the water and get off the pool surface.

Your calcium nodules could be a byproduct of your high calcium. Folks here on TFP who live out west with high calcium and a lot of evaporation (where the calcium doesn't leave, only water does) combat this some by keeping their pH on the low side with a negative CSI.

Calcium Nodules in pools

What are calcium nodules? In swimming pools and spas, they are small mounds, bumps, deposits, or “slag” piles of calcium carbonate which are formed from material that has been released from the plaster. The small calcium nodules are rough to the touch, hard, and generally gritty. Nodules may...

www.troublefreepool.com

Please keep all your posts on water chemistry here.... better for us to get the whole picture. Thanks.

Maddie

 

[RANDY M]

I always keep my CSI stable and add liquid chlorine and acid slowly in front of a jet in deep end. Stabilizer in a sock in skimmer.
The boric acid I brushed and ran pool cleaner.
I keep my pH around 7.8 because it rises much faster when its any lower. My pH still rises the same even after boric acid. Maybe I didn't add enough.

 

[RANDY M]

Hi,
I swear my pool didn't look like this 2 months ago. My wife agrees. Looks like mottling to me.
Re-plastered 4 years ago. Partial drain 2 months ago to lower calcium. Added 55 lb boric acid 6 weeks ago to try to slow pH rise.
I always try to keep CSI between -.2 and .2. Add chlorine and acid slowly in front of jet in deep end.
Any idea as to what happened? Could boric acid somehow do this? I brushed after adding it.

FC – 5
pH – 7.8
TA – 65
CH – 650
CYA – 40
SALT – 2200
Borate – 38
CSI - .13

 

[Poolbreh]

your numbers don’t look that bad the ch looks high and some of the pictures make it difficult with the trees reflections. Better ask the man. @onBalance

 

[onBalance]

I do not see any evidence of "calcium nodules" in your photos. Calcium nodules are random and are significantly raised and rough compared to the plaster areas around the nodules.

I have never seen "gray mottling discoloration" take four years to show up, and typically that is a potential white plaster problem and issue that turns a gray color within the first year.

You indicate that the color of the plaster is medium gray. Therefore, what may be happening is that the gray color plaster has turned somewhat whiter in color over the past the four years, and now perhaps there has been a removal of the whitish deposit and exposing the original darker gray color.

Boric acid is somewhat acidic and could have dissolved some of the plaster surface (and natural calcium scaling) and make a change to the appearance of the plaster surface. This is my thinking, but I need your input on this possibility. Study the areas that are darker and lighter and see if any patterns or reasonable possibilities become evident.

 

[RANDY M]

I do not see any evidence of "calcium nodules" in your photos. Calcium nodules are random and are significantly raised and rough compared to the plaster areas around the nodules.

I have never seen "gray mottling discoloration" take four years to show up, and typically that is a potential white plaster problem and issue that turns a gray color within the first year.

You indicate that the color of the plaster is medium gray. Therefore, what may be happening is that the gray color plaster has turned somewhat whiter in color over the past the four years, and now perhaps there has been a removal of the whitish deposit and exposing the original darker gray color.

Boric acid is somewhat acidic and could have dissolved some of the plaster surface (and natural calcium scaling) and make a change to the appearance of the plaster surface. This is my thinking, but I need your input on this possibility. Study the areas that are darker and lighter and see if any patterns or reasonable possibilities become evident.

Thanks for your input. I do appreciate it.
Now we think the gray plaster turned white. (evidently we don't know what are pool looked like; old age memory?)
The spa is a uniform gray and all the sides of the pool are too.
I threw the boric acid in walking around the pool and I don't think I ran the pump for 24 hours. But I did brush at least once. Could it have bleached the plaster? I'll try to get a better picture without tree shadows when the wind stops blowing.
My calcium was 1100 before a partial drain and I had the TA and pH a little lower to keep the CSI in the parameters.
Of course I have to ask if there's a solution for it besides re-plaster.
Thanks again

 

[onBalance]

If the gray plaster color has whitened during the past 4 years, then it will likely do it again. That is what typically happens to colored plastered. There is no need to re-plaster.
The boric acid probably dissolved and remove the white calcium scale in certain areas which resulted in the contrast of color.

 

[RANDY M]

Thanks. I'm still trying to get a decent picture to show how the whole pool is blotched. In the attached picture the white plaster color on the left gets narrower and goes the length of the pool. There's a jet in the shallow end right below the rock that points in that direction. As you can see half the shallow end is white and the other half, walls and steps are gray. Just grasping at straws here.
If the gray plaster faded would it it be more uniform? What are the chances of the white turning gray again? At this point the pool just looks ruined. Thanks for your help.

 

[onBalance]

Please understand that I am still not totally sure what has occurred with your pool.
My guess is that the original gray color had been covered by a thin layer of a white calcium deposit, and now some of that calcium deposit has been removed to exposed the original gray color. It is then likely that the recently exposed gray color will probably turn white again and then the entire pool may end up more uniform in appearance.

On the other hand, you may want to consider having a drain and acid wash to remove all of the white calcium deposit and restoring the original gray color. Of course, in time, the entire plaster finish will probably lighten and turn whiter over time. But it would likely be more or less uniform, just like it was prior to two months ago.

 

[RANDY M]

That would be great if it became even a little uniform in time.
So it's possible that the white sections in the pool now could be a thin layer of calcium over the original gray?
If I rubbed it with a pumice stone I might see gray plaster?
Thanks again for all your responses, I'll try not to ask any more questions (maybe 1 or 2)