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New Plaster: Cracks and Discoloration

Posted by dshlaw (My Page) on
Wed, Apr 13, 11 at 14:42

My new plaster is a week old and is developing some small cracks on the seat and steps and has some color variation, particularly in the spa seat, that I'm not sure whether I should accept. Also, my chemistry doesn't seem to match the plaster start-up instructions my PB emailed to me on plaster day. I welcome any of your expert advice on whether these are problems and how I should deal with my PB.

The chemistry is as follows:
alkalinity: 210
PH: 8+
Cyanuric Acid: 86
Free & Total Chlorine: 0
Calcium Hardness: 400+
Phosphates: 1,000+

Picture of cracks on seat:
Plaster Cracks

Discoloration in Spa:
Seat Discoloration

Follow-Up Postings:

RE: New Plaster: Cracks and Discoloration

Get the pH down to 7 to 7.2.
Where did you get the water from that it has phosphates?
Who added CYA this early?


RE: New Plaster: Cracks and Discoloration

Scott, I'll advise my PB to lower the PH.

The water came from the tap at my house (in Mississippi). The pool store where I had the water tested said that phosphates are in our tap water for some reason and that you have to use phosphate remover before using chlorine.

Regarding the CYA, if it was added, my PB added it. The instruction sheet my PB provided to me from the National Plasterers Council says: "after the 4th day - adjust CYA levels to 30 to 50 ppm based on the primary sanitizer of the pool..." I was assuming, but now doubt, that my PB was following these instructions.

What is your opinion on my plaster discoloration and cracking problems? Thanks in advance.

RE: New Plaster: Cracks and Discoloration

Plain plaster? What brand? Have you been brushing?

Do you have a salt cell? I prefer to see CYA at around 70 with a cell.

New plaster takes a few weeks before it's ready for CYA though this isn't what is causing the cracks to appear. However, when it comes time to start slowly introducing your pool to chlorine, it will make it harder to get the FC level to where it will be effective.

I typically introduce a freshly plastered pool to chlorine by using tablets. They would slowly add CYA as they erode.

Lowering the pH and brushing may or may not remove the visible cracks. These are typically caused by shrinkage. The shrinkage may be caused by being exposed to the air and wind while waiting for the water to rise or from a batch of plaster with too much water in it, the latter being less likely but still possible.

There two types of chlorine you may add now with the CYA this high, liquid or lithium hypochlorite powder. Liquid comes either in 10-12% from a pool store or 6% Clorox or it's equivalent It must be unscented. Wal Mart has Great Value and is sometimes less money. Some super markets may carry a store brand. If it's labled 6%, it's fine too.

Lithium powder is quite expensive, more so than bleach.

Use the Pool Calculator to determine how much to add. Algae treats phosphates like Miracle Grow. Start adding bleach to get to 3% of the CYA level for a week, then up it to 7 % the following week and 10% after that. If you have a salt cell, after the plaster is a month old, dial in the cell so it will produce enough to hold your FC at 6% of the CYA level. Removing phosphates is not normally needed but you do need to be aware and keep the FC levels up

CYA doesn't leave except by dilution. At some point, some water will need to be removed and replaced. Your plaster is still too green to do this yet. Wait till it's six weeks or older. This is normally the last thing added, not the first. Who ever added it screwed up.

Keeping the chlorine level up will kill algae before it has a chance to feed on the phosphates.


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