Pool Plaster is a mess HELP!

[jblizzle]

Welcome to TFP!!!

Your pictures are so out of focus it is impossible to draw any conclusion from them.

What is wrong with the plaster? Is it discolored? pitting? rough?
What happens when you brush?
How have you chlorinated? With the high CYA I am going to guess with trichlor tablets. These also tend to lower the pH.

With the low CH you are reporting (not sure how a change from 120 to 200ppm was possible) and if your pH was consistently low as you earlier seemed to indicate. Then your water would have been VERY corrosive to the plaster and pulling the calcium out of the finish and making it rough.

If the plaster is damaged, there is nothing chemically that is going to fix it. We can however help you balance the pool to keep it from getting worse.

The high CYA is not related to the plaster issues directly, but it does indicate a potential problem going forward in keeping your pool algae free.

 

[SunnyOptimism]

Your calcite saturation index (CSI) is -0.68

A negative CSI less than -0.6 means that your water is corrosive to plaster like @jblizzle said.

Raising your pH to 7.6 and your calcium hardness to 300ppm will drop your CSI to -0.2 which is considered balanced. If you did all that and lowered you CYA to 50ppm, your CSI would be -0.03 which is about as close to 0 as you can get. CYA is acidic and can greatly affect the CSI value.

Any damage done to your plaster can only be repaired at this point by a qualified pool resurfacing company.

My point about FC and CYA was to inform you that your pool water is unlikely to keep algae from forming. We see this all the time in pools that use solid stabilized chlorine products (trichlor tablets and/or dichlor granules). The CYA goes too high, it binds up too much FC not leaving enough to act as a sanitizer and then you get an algae bloom.

Someone will have to actually get in the water and look at your plaster. It is quite possible that your old plaster is roughened and you could have discoloration forming due to algae taking up residence in the roughened surface.


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[azali]

Does this mean it's my pool service's fault?

 

[jblizzle]

That is not for us to decide as we do not know the history.

If your CH and pH were maintained too low (these are the largest contributors to the CSI), then that can certainly cause damage to the plaster.

Good pool services are hard to find .... thus the reason this forum is growing so fast as owners are fed up with the alternatives to maintaining it themselves.

 

[SunnyOptimism]

Does this mean it's my pool service's fault?

That is not at all provable. And even if you could prove it, what difference, at this point, would it make?

We can advise you on how you can get your pool water balanced and sanitary. We can advise you on how to go about getting your pool surface re-plastered. What we do not do is get into legalistic arguments about who is and who is not at fault. Why? Because the opinion(s) of thousands of amateur pool enthusiasts does not constitute a valid legal opinion in any court of law that I am aware of.


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[azali]

Who asked for a legal opinion? I just want to have a talk with him about what he should be checking!

 

[chem geek]

Plaster is composed of calcium silicates and calcium carbonate. The calcium carbonate will dissolve in water that is not saturated with calcium carbonate and it dissolves more quickly with less saturation and lower pH. PoolMath can be used to calculate the Calcite Saturation Index (CSI) and if I plug your numbers into the program it calculates a CSI of -0.86 if I use your first CH number of 120 ppm and -0.67 if I use your second number of 200 ppm. I assumed a water temperature of 85ºF in both cases (a lower water temperature would have an even more negative CSI).

Why did the CH vary so much? Was that with two different test results?

Regardless, the CSI is quite negative and over a longer period of time would degrade plaster. Given the lower pH and the higher CYA level, it sounds like you may be using Trichlor tabs as your source of chlorine. These are very acidic so tend to lower the TA over time and can have the pH be low. When using Trichlor, one would generally have the TA higher, usually in the 100-120 ppm range, but sometimes higher. Also, the CH should generally be higher in plaster pools. Trichlor tabs also increase the CYA level over time making the chlorine less effective unless the FC is proportionally raised. Though the plaster has a mottled appearance, does it feel smooth or does it feel rough? How old is the plaster (even plaster taken care of with proper water chemistry does degrade over time, though can last longer, usually at least 15 and usually 20 or so years or more depending on how much one values the appearance vs. the feel of the plaster).

The blacks spots in your photo look like they might be black algae which can grow when the active chlorine level is low for an extended period of time. I suspect your chlorine level isn't always kept at 8 ppm FC and perhaps it's higher now with the sun lower in the sky but you're using the same number of Trichlor tabs as during peak summer. So if the black spots are algae, then the CYA does have to do with how the plaster looks though technically the spots aren't plaster themselves.

If your pool service is maintaining your water chemistry -- if they are in charge with testing pH, TA, CH, and CYA as well as FC levels and maintaining proper water balance -- then they haven't been doing a good job. They should have maintained the CH higher as well as the TA which would have likely kept the pH higher. Pool services often use Trichlor tabs because they usually only visit a pool once a week, but this has the CYA climb and algae can then grow unless they use supplemental products (algaecides or phosphate removers) to prevent that.

 

[azali]

Thanks, It's going to take me some time to comprehend all of this. I will work on it and then have a chat with Freddy!

The plaster is pretty old BUT, this has happened quickly, getting worse and spreading over a few months.

 

[azali]

Hi,
The CH didn't vary, I just figured it wrong. The pool temp. is in low 70's as I haven't turned on solar. The plaster is rough.
I just looked at pool closely and there is black algae all over! Pool guy won't do anything about it. I'm not sure what to do about it as when I checked the algae remover was not recommended.

 

[jblizzle]

Well, either get a new pool guy or start maintaining it yourself.

There is an article about black algae in Pool School: http://www.troublefreepool.com/content/180-Black-Algae

Rough plaster certainly makes it easier for the black algae to take root.

 

[azali]

I am just looking back over this conversation. The first picture is not out of focus. The discoloration you see is what I'm talking about. The dark spots are a reflection of leaves on the surface. The other pics although yes, a bit out of focus you can still clearly see the problem. What isn't showing up is the black algae all around the tile line.

 

[singingpond]

I would re-read post #22, regarding some corrections that can/should be made to the water so that damage to the plaster doesn't proceed further. Increasing the pH and increasing the calcium hardness are not difficult to do (maybe a friend or neighbor can help you put in the needed chemicals). That's certainly worth doing, while you figure out what to do next and/or who's to blame for the current situation. Adjusting CYA down is more involved, but also important, to allow for better algae control (as well as to improve the CSI number and thereby to protect the plaster from continuing damage).

The pictures in the earlier post all look out of focus to me; the plaster doesn't look uniform in color certainly, but it's hard to see any details beyond that.

 

[azali]

I took some more photos to see if they help.

 

[jblizzle]

Those pictures are easier to see ... although I am not sure what else you want us to tell you.

If the chemistry has been off over the life of the plaster, then the plaster will be damaged. If the pH and CH were too low, then the plaster will be etched. If the pH and CH were too high, you could get calcium scaling. If you have had metals introduced to the water (in tap water, using algeacides, using an ionizer), then you could get dark staining.

 

[azali]

Nothing really, just wanted to try better pictures. Someone is coming by next week so I'll work on where to go from here.

 

[chem geek]

I stopped by azali's house to take a closer look at the pool. More detailed photos you can zoom into are here:

Photo of bottom of pool with pooled-chemical marking
Bench in deep end
In the shallow end
Entry steps
Black algae mostly just below water line

Water chemistry parameters measured as follows (as far as I remember) with the TF-100 that was available:

FC 8.4 ppm
CC 0.0 ppm
pH 7.2
TA 80 ppm
CH 180 ppm
CYA 100 ppm (perhaps a little more, but not much)
Temp 75ºF ?

Calcite Saturation Index (CSI) is -0.75 and since the service person just visited I suspect that with the Trichlor tabs in the floating feeder that the pH might drop more over the week.

I verified that the black spots were black algae -- scraped some off and it smeared green on white paper. With the high CYA, the FC may have been lower most of the time and was only high during this test due to the service person having just visited. The pH and CH are too low as is the TA given the high CYA level -- so the water is corrosive to plaster and may have contributed to the pool plaster condition. The plaster is older (20-25 year?) but the condition is worse than expected even for that age -- not only mottled in appearance but VERY rough and pitted.

The plan is in the short term to get a different pool service that will clean the pool (of leaves, etc.) and bring chlorinating liquid that not only can they dose, but that the pool owner can dose during the week and to stop the use of Trichlor tabs. It is too much for the pool owner to do all the work. The pool will be balanced to raise the CH (to 300-400 ppm) and the pH (to 7.5 to 7.8). The CYA will be lowered over the winter using rain dilution (plus additional dilution as needed) -- the CH will need to be replenished (unfortunately, but that's the way it is with water dilution). For the black algae, the algae will be brushed with a steel brush and the pool SLAMed though at the high CYA level this will use a lot of chlorine (we're under drought conditions so a large drain/refill now isn't a great option). Eventually the pool will need to be replastered, but only after everything is under control with a pool service that will not harm the pool -- at least with the test kit the owner can keep tabs on the pool service.

I don't think the pool is 40,000 gallons. It looks deep, but not very long. I didn't measure it.

 

[Swampwoman]

ChemGeek, I am very relieved for Azali that you are close at hand to help direct this pool recovery There's a special place for you in heaven, y'know!

I look forward to hearing how this one works out.