New Plaster StartUp - Traditional Method - Cold Water LSI Question

[QPSUtah]

I'm trying to advice a maintenance customer that we service whether or not they should replaster this late in the season (I'm in the mountain west).

I've read through this guide

Start-up New Plaster

The first few months are the most criticle for a newly plastered pool. We're here to share best practices to ensure the plaster will last for many years.

www.troublefreepool.com

And I've read this guide

National Plasters Council Procedure | NPT Pool Finishes | NPTpool.com

If you’re a builder, remodeler, or home owner with a brand new plaster pool finish, it’s critical that you follow the steps in this guide to protect and prolong the life of your pool finish. Visit NPTpool.com

www.nptpool.com

And browsing other threads, it seems to be suggested that a slightly positive CSI/LSI is desired for new plaster. If I'm expecting a water temperature in the low 40's, and I target a pH of 7.8, CH of 450, 0 CYA (for now), and Alkalinity of 100, I can achieve an LSI of right around 0. That is slightly outside the range suggested by NPT, which suggests alkalinity of 80 and pH between 7.2 and 7.6, but which would give me an LSI of around -0.3.

Will the plaster still cure fine in this colder temperature? My plaster guy is telling me it shouldn't be an issue, but they don't actually do the start up.

Any concerns with the approach above?

Thanks!

 

[ajw22]

Plaster Installation and Maintenance - Further Reading

www.troublefreepool.com

Plaster Start-Up Guides - Further Reading

www.troublefreepool.com

@onBalance has written that the normal CSI guidelines are not applicable to new plaster finishes under 30 days old. It is actually necessary, to achieve a smooth and dense surface, to have about a +0.5 CSI during the first 30 days. This is because the plaster (cement paste) surface contains about 20% calcium hydroxide, which is somewhat soluble in balanced and slightly positive CSI water and can be dissolved away. The plaster surface needs to be "carbonated" before the CSI should be lowered to the acceptable and balanced range. And that generally is achieved during the first month under balanced water.

Will the pool be left open for the winter and the water chemistry and pH adjusted as necessary?

I would not plaster a pool and then shortly after close it.

 

[QPSUtah]

Plaster Installation and Maintenance - Further Reading

www.troublefreepool.com

Plaster Start-Up Guides - Further Reading

www.troublefreepool.com

@onBalance has written that the normal CSI guidelines are not applicable to new plaster finishes under 30 days old. It is actually necessary, to achieve a smooth and dense surface, to have about a +0.5 CSI during the first 30 days. This is because the plaster (cement paste) surface contains about 20% calcium hydroxide, which is somewhat soluble in balanced and slightly positive CSI water and can be dissolved away. The plaster surface needs to be "carbonated" before the CSI should be lowered to the acceptable and balanced range. And that generally is achieved during the first month under balanced water.

Will the pool be left open for the winter and the water chemistry and pH adjusted as necessary?

I would not plaster a pool and then shortly after close it.

The plan was to let it cure and brush for 30 days or so, and then close for the season. So it would be mid December at that point. Also, that's still assuming the "traditional method"? Also, this will be a re-plastering, but I suppose that still qualifies as a new plaster finish.

Maybe @onBalance will chime in here. But yes, at 40 degree water temperature, I'd need to boost pH to 8 and Alkalinity to 200 for the 30 days to get close to +0.5. Would still be okay for the pump?

But yes, perhaps the wise choice would be to do in the spring.

 

[ajw22]

I would wait until the Spring to plaster.

I believe a pool should be open and water chemistry maintained for at least 6 months after plastering. The 30 day start-up is only the beginning of the plaster curing completely.

 

[onBalance]

What is the pH, TA, and CH of the tap water that will be used to fill the new pool?
As was mentioned to you by ajw22, it is risky and problematic to newly plaster and then close the pool soon afterwards.
In my opinion, the NPC startup procedure contradicts itself repeatedly and is not the best program to follow for new plaster.