Re-plastered pool continues to produce erotion spots

[johngee]

Three years ago I had my in ground pool re-plastered buy a reputable pool company and when finished it looked great.
About a year and a half ago I noticed some discolorations on the steps. Upon scratching them with my finger nail I noticed that the plaster had disappeared and what I was seeing was the sand which the plaster contains. I had it looked at by the pool refinishing company and they told me it was the stabilizer I used. Without getting into that, we have not established that to be fact, especially since I used BioGuard tablet chlorine. Since then the pool has blossomed with this surface erosion on better than half of the pool and all over the spa. I’m looking for someone who might have experienced the same thing, and/or an expert in this field who might be able to give me advice as to how to move forward. I’m wondering if the plaster composition could have been defective, or the method of finishing the plaster might be in question. As I see it the only way to fix it is to re-plaster the pool (again).

 

[zea3]

Hi, welcome to TFP! I am sorry you are having this problem with your pool. Could you please post a complete set of current test results? Test results will help us rule out some potential causes. Also if you can post pictures of the problem areas that may help too.

 

[JasonLion]

Welcome to TFP!

The effects you describe could be from defective plaster or they could be from improperly maintained chemical levels. If you post a full set of water test results we can tell you what is going on in this case.

 

[PoolGuyNJ]

In addition to using the BioGuard tablets, what else have you been adding to the pool?

Scott

 

[johngee]

First let me thank you for your quick response. I’m going to combine all of the questions here and respond with this reply. Let me add more baseline info. I have had this pool for 27 years and have always done my own pool service. I got 22 years from the original plaster before it started to blister from old age, and this problem started 2 years after it was done. Pool size is 14K gallons and last spring I drained half the water and refilled it because the erosion problem was continuing to grow.

1. Complete set of test results from a national pool store
a. Free Available Chlorine – 6 (coming down from super chlorination)
b. Total Available Chlorine - 6 (coming down from super chlorination)
c. Cyanuric Acid – 70
d. pH – 7.3
e. Phosphates – 300

2. Scott asks what else I have put in the pool:
a. I used a Pentair 320 inline chlorinator which uses 3” tablets for many many years. I now use only liquid chlorine and acid. To reduce Phosphates, I used PhosFree and aside from those three the pool has had no other chemicals add to it.

3. I have added two pictures that articulate the condition. What is important is that the problem is continuing to become worse and has not stopped. In picture 667a you will see two white spots. Those spots are white epoxy placed there by the pool refinisher over a year and a half ago. Notice the discoloration around the outer edge of the epoxy. That is the erosion of the plaster which was not there when it was done. The pool is a combo pool/spa. The spa also has the erosion but the pool, although the worse of the two, only has it on half of the pool. The other half is only sparsely affected.

 

[johngee]

After further thought two things arose.
1. I have put sodium bicarbonate for Alkalinity adjustment.
2. For some reason I didn’t send the second picture so here it is.
Thanks for your generosity

 

[zea3]

Hi, do you have test results for Calcium and total alkalinity?

 

[johngee]

I sure do. I should have included it.
1. Total Alkalinity - 90
2. Calcium Hardness - 300 with pure tap water being 60

Hope that helps.

 

[JamesW]

It looks like classic "spot etching" to me. If it were only aggressive chemistry, then the etching would be more uniform. Aggressive chemistry would accelerate the etching. The history of the chemistry from the time it was applied until now would be necessary to determine how much the chemistry affected the speed of the etching.

There is no fix other than replastering. Increasing the CSI would slow the progression of the spot etching, but it won't stop it.

http://www.poolhelp.com/emails.aspx

 

[johngee]

JamesW,
I want to thank you for your response and especially the link to the emails. What a wealth of information. Is there a way I can contact someone the onBalance? I would like to have some further discussions with them about some of their findings, as well as find a way I can test my plaster for this phenomena . Some of the findings are exactly what I suspected but it is hard to come to any conclusions until I can establish the authenticity of their findings.
Again, thank you for your help.
John

 

[JamesW]

member29692.html

 

[duraleigh]

Johngee,

Do the tiles imbedded in the steps have the same types of spots? It sorta' looks like it from the pics.

 

[johngee]

Dave S.
Yes but not all of them. Maybe 50% or more. Picture 667a really shows the one of the worst areas on the steps. I really believe what I have here is spot etching. Be happy to chat with you over the phone if you were open to it.
John

 

[JamesW]

Were the tiles originally one solid color? It would be unusual for ceramic tile to be affected by chemistry.

 

[duraleigh]

If the tiles exhibit the same symptoms, then I would eliminate etching of the plaster as a cause. Ceramic doesn't behave that way.

 

[johngee]

No the tiles were not one solid color and I can state that they have not be affected by this problem. Now the plaster around them is a different story.

 

[johngee]

It has been brought to my attention that there may be some confusion regarding the tiles and if they were solid blue when originally installed.
The answer is no. What you see is what they looked like when originally installed.

 

[onBalance]

Hi Johngee,
I am a member of onBalance (there are 3 of us). I want to help and I will try to answer your questions. I guess you could ask them here on your post, or you could PM me, whichever is best and is okay by TFP.
JamesW gave you correct info. Is it not caused by the stabilizer (cyanuric acid), that is simply an incorrect claim, misdirecting away from a plastering issue. It appears that the pictures show that either dirt or iron has discolored the spotted areas slightly brown due to the severe porosity. Things stick better to porous surfaces. We have been studying this spotting issue for over 10 years. We have had two professional cement labs and researchers (with PhD's) help us to determine and document the actual causes of "spot etching" or what more accurately is defined as "white soft spotting."

 

[johngee]

Hello 'member of onBalance'
Let me say thank you for your generosity first.
Second, let me give you, and others, some clarity on what you see in the pictures. Those spots you see are tan colored sand.. It is the sand that makes up the plaster that was applied to the previous wall. They appear to be darker because I didn’t brush or clean them before I took the pictures. Had I done that, the spots would have been lighter in color. But let me clear, the smooth plaster is gone which is exposing, as a concaved spot, the sand below where plaster once was. It is a perfect place for algae to grow.
John

 

[onBalance]

I forgot to tell you my name is Kim, and I am a former pool plasterer many years ago.
Pool sand or aggregate is an off-white color. I think the fact that the smooth plaster part is gone indicates an advanced stage of this erosion problem. Were the spots smooth when first noticed and now are more rough to the touch? I would think that the spotting would have been visible within the first year. Yes, no?
I am hoping that you have some records to show that you informed the plasterer at the beginning of all this. I am curious what state you are located in, but some states have a contractors license board that you could contact and ask for an inspection. I can provide some literature to you that would help inform the agent if he isn't familiar with this problem. I have worked with some CA and AZ agents in the past.
Essentially, the spots can be caused by a combination of things and the degree of abuse. First, the plasterer usually adds too much calcium chloride to the mix, then the plaster hardens too fast and they splash water onto the surface to soften up the plaster which weakens certains areas of the plaster surface. Then over time, deterioration takes place and (balanced) water will dissolve the weak and soft cement material (back into the pool water) causing increased porosity of those areas or spots. Interestingly, your plaster does not look like a lot of calcium chloride was added, but that doesn't change the final outcome if true.