Plaster Delamination

[robertb]

Hello Everyone,
I have an in ground pool that I had replastered 4 years ago. I drained it in the spring this year as the CYA level was around 130 and filled it with fresh city water.
About a month after filling it I noticed 4 areas on the top step that the plaster has started to flake off.
I called the pool company that did the job as I have a 10 year warranty on the plaster. The supervisor of the warranty division came out to look at the plaster.
His explanation for the plaster flaking was that he guessed that I had very high CYA levels, probably in the 250 - 300 range. The reason for this would be that the chlorine dispenser tends to float near steps in the shallow end and therefore the CYA would be much higher there, causing the plaster to etch and be weak. He also pointed out that the steps have a grey mottle pattern which he said was etching due to the high CYA. I had noticed that pattern before but thought it was the natural pattern of the plaster as it cured.
As I have refilled the pool the chemicals were all in perfect range when he tested the water.
However, for the 3 years before draining and refilling it I would test the water myself with test strips every few days and also take it to Leslies pool to test about once every 2 weeks. I have a few of the read outs from Leslies and the CYA was always in the 100 -120 range according to their tests.
I'm about to call the Pool Company out again to do the repair as it was too hot in phoenix to do it this summer and he asked me to call back in the winter time.
The options he is giving me are that he touches up the areas that have flaked, but the repair will be obvious due to the plaster being different, or he did suggest that they could tile all of the steps for the cost of materials and labor.
The grey mottled pattern seems to be worst on the steps although there are some streaky looking patterns running down the wall in one area of the pool.

My question here is
1 - could high CYA cause etching and delamination of the plaster or is he feeding me a story.
2 - Does it sound like the grey mottle pattern and flaking are a construction defect rather than a chemical reaction
3 - what should I expect for a warranty repair of this type. Should I expect them to just touch up the areas that have flaked off and just deal with the different color of the plaster?

I have attached a couple of pics of the steps and highlighted on the top step the 2 biggest areas where the plaster has separated.

Thanks in advance for your advice and input

rob

 

[pooldv]

Welcome to TFP!

I have never heard of high CYA causing etching or delamination.

Delamination is typically caused by poor surface prep, more here, Diagnosing Pool Plaster Problems

Etching is caused by aggressive water, typically through low PH, low TA or low CH or some combination of those being low. Trichlor pucks can certainly contribute to low pH, especially in pcalized areas. More here, Pool School - Calcium Scaling

I have asked for some more expert feedback on the possibility of CYA contributing to this but I am going with no for now. Yes, they will patch the affected area and the color will probably not exactly.

 

[JamesW]

Delamination won't be a chemistry issue because the chemistry won't go through the entire plaster. Delamination is likely due to exposed plaster overheating or application issues.

Tab use often causes low ph and TA, which can cause etching. High CYA can affect CSI if not accounted for. A high CYA can mean that the carbonate concentration is lower than it would be at the sameTA and lower CYA.

 

[gwegan]

Most CYA tests lose accuracy at levels above 100. I would have doubts about the reliability of CYA test results above 100. Your level could have been much higher.

That said delamination is usually related to application or physical issues with the plaster, not chemistry.

 

[bdavis466]

Is the delamination you are referring to thin sections of the plaster surface flaking off? Is there still a layer of plaster below the areas that have come off?

I've seen many pools where the top step is especially deteriorated and chronic trichlor use has always been the common denominator. Trichlor is very acidic and can be especially troublesome when the floater gets hung up right above the step for long periods of time.

If the company is willing to repair the issue then I feel they are being pretty generous. If the plaster has actually delaminated, then poor surface preparation is to blame and i would be looking for more to be done than an unsightly patch.

 

[JamesW]

Acid Watch| Pool Spa News | Bond Financing, Water, Water Conservation, Water Quality, Chemicals, Arch Chemicals

There is a study by Arch chemicals from 2004 that concludes that high CYA can damage plaster but I think that the study was flawed and probably biased.

Most likely the damage was from a miscalculated carbonate alkalinity. In fact, if the CYA gets up over 200 to 300, you might not have any carbonate alkalinity at all.

Also, if your plaster was originally white, I think that you have copper staining.

If you drained the pool and the plaster was exposed to direct sun and high temperatures, thay can weaken the plaster's bond to the gunite.

How old is the plaster?

Was the pool replastered over old plaster or was the old plaster removed down to gunite before replastering.

Cyanuric Acid Damages Plaster etc. ??

 

[bdavis466]

I saw you added pictures. The plaster has deteriorated from localized aggressive water. A delamination would be an entire section of plaster that has completely separated from the gunite shell.

 

[robertb]

The old plaster was removed down to the gunite and the plaster is 4 years old
its just the top layer that has flaked off, not all the way down to the gunite.
The tests from leslies don't show any iron or copper in the water.
when I drained the pool in the spring the daytime temps were 80 and nighttime around 60
so, you think it is possible that high CYA could cause the Alkalinity reading to be off and that could cause the damage that has occurred?

 

[bdavis466]

If the damage is localized to the steps then the pucks in the floater are the culprit. If you are having flaking issues everywhere in the pool then the water was allowed to be too aggressive for the long-term. CYA lowers the CSI of the water so that coupled with low pH, TA, and CH resulted in calcium being leeched out of the surface.

What were the typical pH, TA and CH levels?

 

[robertb]

This was from January, a couple of months before I changed the water and were pretty typical:

TAC=5
CYA=120
TA=100
PH=7.6

 

[onBalance]

Trichlor floaters will certainly etch the plaster surface and caused severe pitting and roughness of step areas. Similar to about 40 to 50-grit sandpaper.
I believe I see the flaking in your pictures, and that is not caused by high CYA or aggressive water.
What happened is that the finisher over-troweled the plaster surface (which often occurs when troweling steps) and caused a weakness with a thin layer of plaster just below the surface (about one-sixteenth to one-eighth of an inch). Then when the pool was drained, the plaster dried out a little bit and created expansion and contraction when filled again, and a small area of plaster broke loose in those areas. This is known as "spalling."

I also see copper staining. I don't believe the testing results in that regard. But that issue is independent from the flaking.

 

[pooldv]

Copper and iron tests are often misleading because the metal is in the plaster and not in the water. Or if a sequestrant is present the metal is sequestered and will not show up on the test either. Metal tests only test for metals in solution.

There are only a few sources of copper.
Algaecide containing copper
Alternative mineral "sanitizers"
Copper plumbing or copper heat exchangers that have had copper dissolved into solution due to pH not being maintained at 7.2 or higher