Mosaic Tile Grout Going Soft

[cncs]

Hi everyone, and thanks for a great and informative site.

I have a question and would like to share my pool story at the same time:

We took over the maintenance of the pool that came with our recently acquired house in October, after going through 3 cycles of green algae, shock+algecide and then green hair for our blonde children

The explanation from the pool maintainer didn't seem right, so I found this great site and thought it sounded like overstabilization, so purchased a Taylor test kit and found the cyanuric acid was way off the scale (somewhere between 200-400ppm), and a pH well below 7 (Trichlor tablets heavily in use)

The mosaic tile grout was also soft, and first time after using one of those big Whale brushes the pool became so cloudy you couldn't see your own hand 2 feet in front of you and the cartridge filter clogged up.

So we decided to drain the pool completely and have the tiles regrouted - the contractor did a pretty poor job at removing the old tile grout at first and had to replace nearly 1000 mosaics that got scratched from when the grout was removed, but eventually we got to the point where we could refill, and once the grout had cured and the water was in, the grout was hard and proper.

I took on the responsibility of adding the chemicals, and did the aeration trick and borated the pool, and the water looks great and is quite low maintenance. We've recently added an AutoPilot SWG to get away from Tri-chlor tablets, and are all enjoying the pool and it looks great.

The only minor issue is some stains on parts of the grout which came about when we first chlorinated the pool (I suspect oxidation of the iron in the tap water used for filling)


However, now nearly 2 months after refilling the pool, the tile grout is going soft to the point where you can etch it with a finger nail, and a micro cloud of grout can be seen in the water - saturation index wise I thought I had kept things on the good side, perhaps except for the 7-10 days I was aerating to lower the TA in preparation for the Borate/Borax addition).

So I am not sure if the tile grout used was some inferior product, or if it is purely an issue based on the saturation index of the pool. My question is whether I should add more calcium to the pool (Say bring CH to 325-350) or if it is already a lost cause and regrouting will be necessary at some point.

Pool details:

11500 Gallons / 44Cubic Meters

Taylors test kit

pH: 7.6 (Fluctuates between 7.4 and 7.6 adding muriatic acid as necessary)
FC: 5.5
CC: 0
CH: 275
TA: 60
CYA: 50
Borate: ~50ppm (Calculated, not measured)

Temperature: 27c (From AutoPilot)
Salt Level: 3000 (From AutoPilot)


Best regards and Happy New Year,
Kim

 

[duraleigh]

What is the CH of your fill water?

Where do you live?

Has your pH stayed roughly between 7.4 - 7.6 since you re-grouted?

I doubt it is an inferior grout......most of it is pretty much the same basic ingredients, I think.

 

[cncs]

Hi Duraleigh,

The fill water is CH 250 and the pH is 7.2-7.3

I live in Barbados, and the pH of the pool has been roughly between 7.2 - 7.8 (Mostly between 7.2 and 7.6). While I was aerating it it went a bit more extreme, dipped below 7 and touch 8 a few times, but for short periods of time (Less than 24 hours)

The grouting contractor was talking about the previous batch of grout they were replacing may have been inferior with not bonding agent in it, so that's where I have the notion that grout may not be just grout.

Edit: When I started refilling the pool the TA came to 400ppm (8 drops of Taylor reagent required on the 10ml test), a month later I had it down to 225, and in later november had it around 60 when I had prepared for the Borax addition


Kim

What is the CH of your fill water?

Where do you live?

Has your pH stayed roughly between 7.4 - 7.6 since you re-grouted?

I doubt it is an inferior grout......most of it is pretty much the same basic ingredients, I think.

 

[duraleigh]

Thanks. The pH and CH you report should not be capable of softening the grout. Perhaps in Barbados the quality control is such that inferior grout can be produced. I can think of no other explanation for the deterioration.

The variance in TA for that short period should have nothing to do with it.

Perhaps OnBalance will see this post and comment.....he is the "go to" guy on plaster and grout.

 

[cncs]

Thanks for the input. I had forgotten to post a couple of pictures.

The only two things I am worried about with the pool now is the grout going soft and some staining.

The grout was not that soft when the pool got filled, but maybe it is to be expected in the initial stages (first year?) of a regrouted pool.

The stains came within days of first filling up the pool, around the time chlorine was initially added. At first I thought it might be black algae, but it doesn't feel slimy and putting a chlorine puck on it doesn't make it change color and I couldn't scrub it off because the grout was hard then. Then later on I read on this forum that it could be metal and tried the Vitamin C test - some of the stains came off when I rubbed a vitamin C tablet on the stained grout and thought that was it and it was an metal/iron stain, but now in hindsight with the grout starting to go soft I think it was just me rubbing the grout off and taking the stain with it.

So I am still not sure what I am dealing with stainwise, but I am in mind of scrubbing/brushing the stain off since the grout is now soft, and then boosting the pool CH level to try and counter more leeching of grout/calcium into the water

Best regards,
Kim

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[attachment=1:9bdqcc0h]IMG_2023_resize.JPG[/attachment:9bdqcc0h]

Thanks. The pH and CH you report should not be capable of softening the grout. Perhaps in Barbados the quality control is such that inferior grout can be produced. I can think of no other explanation for the deterioration.

The variance in TA for that short period should have nothing to do with it.

Perhaps OnBalance will see this post and comment.....he is the "go to" guy on plaster and grout.

 

[onBalance]

I see several possibilities for the grout softness.

What type of cement was used? Portland Cement or Plaster of Paris? Or something else?
Did the grout contractor mixed the grout and use for longer than two hours? Did he continually add water to it to make it workable?
And how soon after the pool was filled with water was the 3000 ppm of salt added.

 

[cncs]

Hi OnBalance,

I actually don't know - I believe it was the something else category of grout, but would have to contact him and ask (I don't reside in USA but the Caribbean)

I am sure the grout got mixed and used for more than two hours, but wasn't watching it all day being applied, so don't know about the water addition either.

But he did add something to make it work better as swimming pool grout (A binding of some sort).


Sorry for the lack of clear answers :?

And just apropos an acquaintance of mine mentioned last week that it would have been better to use white tile cement to prevent it from dissolving - a little knowledge can be dangerous

I see several possibilities for the grout softness.

What type of cement was used? Portland Cement or Plaster of Paris? Or something else?
Did the grout contractor mixed the grout and use for longer than two hours? Did he continually add water to it to make it workable?
And how soon after the pool was filled with water was the 3000 ppm of salt added.

 

[carolina pool]

I would agree with onBalance, new grout should go thru roughly the same curing process as new plaster. When you are using bonding agent in the mix it is even more important to let the mix slake, remix and not add any more water after that step. Once it becomes unworkable you have to throw it out and make a fresh batch.

 

[onBalance]

Renovxpt explained it well. It could be bad cement, or the adding of water to a cement mixture after two hours to make it workable will definitely makes the cement weak.
Also adding salt before 30 days also causes the surface of cement to deteriorate. Of course, after 30 days, that should stop.
But I tend to think that it is a bad batch of cement for one reason or the other.
Let us know if you learn any more on what may have happened on your pool job.

 

[cncs]

renovxpt and OnBalance, thanks for your input - the salt definitely was added 30 days after (40-45 days), but sounds more like a mixup happened with the mixing.

A contractor friend of mine (Not the installer) says that most likely it is the Portland Cement type as that is common down here, and explaining your questions to him he was leaning towards the improper mixing scenario as well. He said that you could end up doing 6-8-10 batches easily throughout a day, and that I am quite sure did not happen in my instance.

I was hoping that maybe was just the outer layers of grout that was getting ready to "smoothen out" after a few months underwater, leaving the underneath layers well alone, but seems not to be the case.

I am fed up with contractors (At least around these parts), so this will have to stay like it is for a while can't see myself emptying the pool and reworking this anytime soon.

I've added CalHypo to shock the pool and bring up the CH some more, and will continue to monitor the grout situation

Any ideas on the stains?

Kim

 

[onBalance]

The stains on the tile grout are strange, and I am sorry to say that I don't understand what has happened to cause them. But I will give it some thought and see if I can come up with some ideas later.

 

[carolina pool]

Another common yet wrong process not mentioned previously is using a wet sponge to clean the tile after grouting. This process adds water and weakens the surface as it would with any cementitious finish. When timed properly a dry terrycloth towel is the best way to clean the tile after grouting.

After examining the photos, I would guess the dark spots are the old grout that wasn't removed rather than a stain. It appears that besides the odd yet repeated pattern the only consistent factor is that there appears to be more relief in those areas. This is a guess that would be supported by the weak grout theory coupled with the wire brushing. You should be able to feel the difference.

 

[cncs]

That is a really interesting observation - thanks for that. I also forgot to mention that the grout softness varies in regions around the side of the pool, again supporting the idea of it being badly mixed grout (like water thinned grout), you would think that if it was just water chemistry eroding the grout, then it would be uniform all around the pool

But besides those regular shaped marks\stains the other stains
are right on the surface of the grout and comes out easy with brushing now (because if the grout softness)

My worry with that is just if they are going to keep coming back. And whether I should consider using a sequestration or some other way of preventing them from growing

Thanks