Are these calcium nodules or is this calcium scaling?

bv01

Member
Jun 10, 2020
8
Louisiana
I have several of these big white hard (not brushable) marks on my pool floor. I assume they are calcium nodules since my CH has been very low (160) for too long. I will increase my CH to 350 using a red bag of Joe Melt.

If these are indeed calcium nodules, should I just sand the nodules down and fill the pin hole with epoxy? Anyting else I should do?

Thanks in advance!

PH: 7.4
Chlorine: 6
TA: 70
CYA:70
CH: 160
 

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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
26,288
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
My vote is for nodules.


Let's see what @onBalance says.
 
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JamesW

TFP Expert
Mar 2, 2011
25,741
Definitely nodules.

Is that the original color of the plaster?

How old is the plaster?

Note that the chemistry is mostly irrelevant to nodule formation. Nodules indicate that the plaster is beginning to delaminate. Nodules are a form of efflorescence.

In any case, you should maintain the CSI between -0.3 and 0.0 for optimal plaster longevity.
 
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bv01

Member
Jun 10, 2020
8
Louisiana
My vote is for nodules.


Let's see what @onBalance says.
Thank you for your reply, seems like everyone is thinking these are nodules.
 

bv01

Member
Jun 10, 2020
8
Louisiana
Definitely nodules.

Is that the original color of the plaster?

How old is the plaster?

Note that the chemistry is mostly irrelevant to nodule formation. Nodules indicate that the plaster is beginning to delaminate. Nodules are a form of efflorescence.

In any case, you should maintain the CSI between -0.3 and 0.0 for optimal plaster longevity.
I don't really know how old the plaster is, I bought the house with the pool. The plaster is at least 5 years old, but likely around 10-15 years old. I also don't know if this is the original plaster color, but have always seen the pool in this color and it's colored like this all over the pool.

Do I understand it correctly that I can sand the nodules away and epoxy the pin holes, but that in the long run the plaster should be replaced? I heard pool plaster should last around 20 years before replacement.

Thank you!
 

JamesW

TFP Expert
Mar 2, 2011
25,741
The color looks like copper staining.

You can tell by scraping off a small test spot to see if the color is only on the surface or if it goes all the way through the plaster.

You can scrape off the nodules and seal the crack with epoxy and that should work for a while, but the plaster will eventually need to be replaced.
 

bv01

Member
Jun 10, 2020
8
Louisiana
The color looks like copper staining.

You can tell by scraping off a small test spot to see if the color is only on the surface or if it goes all the way through the plaster.

You can scrape off the nodules and seal the crack with epoxy and that should work for a while, but the plaster will eventually need to be replaced.
Did scrape some at the side, colored turned into a lighter grey, but not a big difference. I will do some more test spots on the bottom of the pool because the more I think about it the more the color of the plaster seems off.

Unfortunately, my pool pump just stopped working like 30 minutes ago. :(
I think it might be overheating (although the breaker doesn't trip) so any testing of plaster will have to be delayed.

Thank you for your elaborate reply!
 

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