Plaster and chemistry

[Wake9909]

Hi guys! Thank you for the wealth of information you provide on this website!!

My gunite/plaster pool is approximately 9 months old now. I’ve noticed these cracks in my plaster on the seat in the deep end (see pic attached). I don’t really notice this happening nearly as much anywhere else in my pool. Is this normal?

Also, is it more important to keep the CSI where it needs to be or keep the pH down? It seems like lately the higher pH yields a more balanced CSI, based on all my chemistry. Previously, I was told to not let my ph exceed 8.0. Now, with colder temps, a pH of 8.0-8.2(ish) yields a more balanced CSI. Thoughts?

Thanks in advance!!

 

[RMcGirr83]

That looks like plaster crazing. @onBalance ?

 

[Wake9909]

That looks like plaster crazing. @onBalance ?

What’s that mean?

 

[ajw22]

Was your pool plastered on a hot day?

It looks to me like shrinkage cracks caused by the plaster drying out prematurely before the fill water got up to the level of the step.

 

[Wake9909]

Was your pool plastered on a hot day?

It looks to me like shrinkage cracks caused by the plaster drying out prematurely before the fill water got up to the level of the step.

It wasn’t hot when it was filled. It was around the beginning of March.

 

[onBalance]

Yes, this is severe plaster craze cracking. It can be caused by several different issues. Such as: plastering during a windy day, or a hot and dry day, or from adding too much water to the plaster mix (a high water/cement ratio), or by adding too much calcium chloride (hardening accelerator). It is unfortunate. The only possible remedy is by power sanding.
If the CSI is balanced at a high pH, a pH of 8.2 won't hurt anything.

 

[Wake9909]

Yes, this is severe plaster craze cracking. It can be caused by several different issues. Such as: plastering during a windy day, or a hot and dry day, or from adding too much water to the plaster mix (a high water/cement ratio), or by adding too much calcium chloride (hardening accelerator). It is unfortunate. The only possible remedy is by power sanding.
If the CSI is balanced at a high pH, a pH of 8.2 won't hurt anything.

Is it possible to be only in that one location and not throughout the entire pool?

 

[duraleigh]

I do not think a pH of 8.2 is good practice. Many phenol red tests only go up to pH 8.0 - 8.2 so it puts you at the upper limits of your testing capability and possibly not being able to tell when you exceed it.

Depending on the make up of your fill water, you may not need to be concerned about csi at all. Can you tell us the CH and TA of your fill water?

TFP does not suggest you maintain your pH above 7.8. Certainly, those with years and years of experience with pool water chemistry can push the "edges" of many things we teach......pH included. That does not say it is good practice for the majority of us.

 

[onBalance]

Wake9909, yes craze cracking (which are actually "shrinkage" cracks) can occur in just one area of the pool. One of the various batches of pool plaster can be mixed improperly, or that they over troweled and added water to only that area of the pool which then causes plaster shrinkage.
There are somewhat inexpensive pH meters that can accurately test various pH levels at any range so that you can accurately determine and keep your CSI in the proper balanced range for plaster-based pools.

 

[Wake9909]

Wake9909, yes craze cracking (which are actually "shrinkage" cracks) can occur in just one area of the pool. One of the various batches of pool plaster can be mixed improperly, or that they over troweled and added water to only that area of the pool which then causes plaster shrinkage.
There are somewhat inexpensive pH meters that can accurately test various pH levels at any range so that you can accurately determine and keep your CSI in the proper balanced range for plaster-based pools.

Can craze cracking cause an actual pool leak, or is it primarily cosmetic?

 

[ajw22]

Can craze cracking cause an actual pool leak, or is it primarily cosmetic?

It is cosmetic on the surface of the plaster. None of the cracks should go through the thickness of the plaster to leak.

 

[Wake9909]

It is cosmetic on the surface of the plaster. None of the cracks should go through the thickness of the plaster to leak.

Good deal. Glad to hear that! Thanks!

 

[TXaquaholics]

[deleted]

 

[Wake9909]

@Wake9909 Curious how this was resolved. I have a problem where the calcium chloride concentration was too high during a replaster job. Significant grey mottling throughout the pool and spa with some craze cracks. Did the plaster company chip out/remove the problematic plaster or just replaster over it?

Honestly, we didn’t do anything about it. It’s my understanding it’s just something that happens sometimes, and ours doesn’t seem horrible, so we’re just living with it.