Calcium Crack in Plaster

johnjmattingly

Active member
Apr 2, 2021
30
Austin, TX
Pool Size
27000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi all,

Today when opening the pool and testing the chems, I noticed a crack in my plaster that seems to have been caused by calcium leaching. Please see photos attached.

When I checked the chems, everything was as I had left it at last check several weeks ago, except for my pH which was off the charts. FC 6.5, TC 0, TA 65, CH 750, CYA 30, pH off scale, likely as high as 10 or 12. This puts my CSI at -1.00, ugh. I'd been keeping my pH in check due to my high CH, and was able to keep my CSI in the zone no problem. Seems like this pH spike was perhaps a tipping point.

I'm not worried about leaks. When we excavated, we literally made jokes with the builder about how we didn't even need to concrete the pool, since it was sitting in a bed of solid limestone. But, I would appreciate some advice about how bad this might be and what I should do about it. Looks like I'll be doing a partial drain once my FC drops in order to mitigate my high CH. Anything else I need to do here, specific to the plaster itself?

Thanks!
 

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Hi all,

Today when opening the pool and testing the chems, I noticed a crack in my plaster that seems to have been caused by calcium leaching. Please see photos attached.

When I checked the chems, everything was as I had left it at last check several weeks ago, except for my pH which was off the charts. FC 6.5, TC 0, TA 65, CH 750, CYA 30, pH off scale, likely as high as 10 or 12. This puts my CSI at -1.00, ugh. I'd been keeping my pH in check due to my high CH, and was able to keep my CSI in the zone no problem. Seems like this pH spike was perhaps a tipping point.

I'm not worried about leaks. When we excavated, we literally made jokes with the builder about how we didn't even need to concrete the pool, since it was sitting in a bed of solid limestone. But, I would appreciate some advice about how bad this might be and what I should do about it. Looks like I'll be doing a partial drain once my FC drops in order to mitigate my high CH. Anything else I need to do here, specific to the plaster itself?

Thanks!
Why do you think it’s caused by calcium? CSI that’s off for a few months isn’t going to cause cracks. I thought calcium leeches from plaster when it’s too low.

More likely you have a leak in that return and that’s caused some settling.
 
Last edited:
I suggest you contact your builder and put in a warranty claim for cracking on your 3 year old pool.

Water chemistry does not cause cracking like that. The crack is caused by a structural problem. We have seen many cracked pools in the Austin TX area.
 
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Why do you think it’s caused by calcium? CSI that’s off for a few months isn’t going to cause cracks. I thought calcium leeches from plaster when it’s too low.

More likely you have a leak in that return and that’s caused some settling.
I was thinking calcium due to the white substance protruding from the crack. Figured that was leaching.

Appreciate the feedback. I'll get in contact w/ the builder.
 
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