Pool water imbalance. Cloudy, algae, pool tiles coming loose.

[Blew]

Hi all,

We have a fully tiled concrete pool built circa 1970 that's having some trouble this summer in Sydney, Australia. I'm finding the tiles are coming away from the pool surface in various places. This has happened before but not anywhere near as frequently as this summer. We bought the house three years ago and the previous owner left a stash of missing tiles behind, so it's been a problem for a while, but I'm not sure how frequently they fell off before we purchased it.

It may have something to do with the water imbalance. I've recently discovered that the CYA test on all the test strips I was using over the past year is not reacting to CYA properly, so I've added far more CYA than I should have! I've had a lot of issues with cloudy water, algae (or pollen?), and fluctuating PH, which I assume is because of the CYA. We've had quite a bit of rain in Sydney this summer, but I've not had this issue during the previous very rainy summers. I only realised that the CYA test wasn't working when I purchased another cheap strip test which showed high CYA, so I had the water tested by a pool shop which showed the same results. I then tested the same water with two other test strips, one of the exact same brand as I was using, and both were consistent with the pool shop and cheap test strip results. Lesson learned for using test strips I want to get a decent test kit instead.

So, I'm planning on draining a lot of water from the pool and replacing it to rebalance the CYA, then repair the pool tiles. Quite a few tiles have come loose from the bottom of the pool, but I don't want to drain the entire pool to replace the tiles if I can help it. Before I do that, I wondered if I could ask the experts here a few questions to make sure I'm on the right track.

* Is the high CYA likely the cause of the tiles coming loose, or is that a red herring? The Poolmath app says my CSI levels look good (!?!?)

* What's the best way to repair the tiles underwater? The previous owner seems to have used epoxy but I'm not sure if that's the best option. Most posts I can find on this forum mention waterline tiles and draining the pool a little, but I really don't want to drain the entire pool.

* I also find sand in the Polaris cleaner bag, which may be from the grout, but could also be due to a pool filter issue (sand filter). Thoughts?

Latest test results are below:

TA: 12.05
FC: 12.05
CC: 0
pH: 7.2
TA (adj): 20.33
CYA: 134
TH: 162
CH: 162
Phosphates: 0
Copper: 0
Temperature is around 26-30 degrees Celcius.

Any help would be much appreciated!

 

[ajw22]

Welcome to TFP.

High CYA does not cause tiles to come loose.

Water getting behind tiles through cracked grout lines will erode the thinset holding the tiles over time.

You need to get a complete test kit from Clear Choice Labs to accurately know and manage your water chemistry.

@mgtfp @AUSpool may be able to advise you on testing and chemicals.

I suggest you review…

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

 

[mgtfp]

Welcome to TFP!

As Allen said, CYA has nothing to do with it. Tiles are probably already quite loose. Once the first tiles are off it gets easier and easier for water to get behind other tiles and flush them out.

Not quite sure if there is an underwater repair method. I reckon with a 50 years old pool you are looking eventually into a full reno.

In the meantime, get a test kit from Clear Choices Labs and get pool water maintenance sorted.

 

[Blew]

Thanks. Would the low calcium hardness be a factor in the tiles coming loose? I read that the water would leech calcium from the pool if it's not high enough, so I'm wondering if it's worth spending the money on calcium replacement once I've sorted out the CYA and other chemicals.

 

[mgtfp]

It's not CH on its own, it's the CSI or Calcite (Calcium Carbonate) Saturation Index. CSI needed to be low for a long time. That would have been under the watch of previous house owners, nothing that you could have done that wrong in such a short period of time.

I don't really trust the pool shop tests. I'd suggest to get a Clear Choice Labs test kit, run and post a full set of tests, and use PoolMath to calculate the CSI.

The test kit may look expensive at first sight, but being independent from pool shops will save you lots of money, and compared to the 100k$ value of a pool it's a very small investment to maintain the value of your pool.

 

[Blew]

It's not CH on its own, it's the CSI or Calcite (Calcium Carbonate) Saturation Index. CSI needed to be low for a long time. That would have been under the watch of previous house owners, nothing that you could have done that wrong in such a short period of time.

How long is a long time? I fear the CYA may have been too high for almost a year. The CH must have been very low for at least the three years we've been here, as I wasn't testing for it before now. It was a deceased estate and the agents had to get someone in to clean the pool before we moved in, so there's a chance they replaced the water at that time which lowered the CH. Otherwise it must have been low for a lot longer than three years.

I don't really trust the pool shop tests. I'd suggest to get a Clear Choice Labs test kit, run and post a full set of tests, and use PoolMath to calculate the CSI.

The test kit may look expensive at first sight, but being independent from pool shops will save you lots of money, and compared to the 100k$ value of a pool it's a very small investment to maintain the value of your pool.

The problem is the reagents only last a year, and unfortunately we don't have a lot of spare cash at the moment. So I was thinking of a simpler test kit for the rest of this summer, since we're already half way through, then buy the CCL around October to prepare for next summer.

The Poolmath app currently says the water is ok at 0.0, but only after I input the CYA. If I set the CYA to 0 then it says the water is corrosive at -1.19. It seems like the accidental CYA overdose balanced out the lack of CH? Does a CSI of 0 mean the water won't corrode the grout etc regardless of the chemical numbers?

The pool shop test does broadly correlate with the three other test strips I used, which all show high CYA along with general consistency in the other chemicals. It may not be 100% accurate but, given the CYA numbers are on the extreme end at the moment, I figured the accuracy is not important until I replace the pool water. The pH increases every time it rains, so I've been adding dry acid to bring it down. That has mucked up the TA too, and adding chlorine didn't do anything. I couldn't figure out why until I discovered the CYA was so high!

I'm currently draining the pool to rebalance the CYA. How important is it that I add calcium once I replace the water? It's going to cost about $100 in calcium just to get it to about 400.

 

[mgtfp]

CYA only has an indirect effect on CSI. The CSI is basically the product of the Ca²⁺ and CO₃^2- concentrations and then the logarithm of it. The Ca²⁺ concentration is basically CH, just some unit fiddeling, and the CO₃^2- concentration can be calculated from TA, but other Alkalinity contributions have to be subtracted, which is mainly CYA.

That pool is old, any damage is done, don't fret about it.

Yes, it us important to rebalance calcium after the fill. Maybe get TA to about 80, CYA around 40-60, then adjust CH so that CSI is about neutral in the relevant pH range.

 

[AUSpool]

Geday Blew and welcome to TFP,

I have an older pool with ongoing tile issues too. I believe a lot of it is down to the adhesive and grout that was used. Ive used a product from Dunlop for underwater repairs but it’s messy, don't overwork it and don't expect an ‘as new’ finish. The Dunlop underwater adhesive will provide the the grout in one application. I would speak to someone in a tile shop with regards to adhesives and grout for above the waterline.

Browse Dunlop Tile All Plus - Dunlop Trade

Dunlop Trade's Tile All Plus product is a versatile tile adhesive that is suitable for various tile types. View now and get a reliable bond for your next project.

dunloptrade.com.au

The clowdy issue is from low free chlorine, FC, or rather a low FC/CyA ratio. TFP treats FC as being dependant on CyA, this is supported by the chemistry but mostly ignored by the industry. It’s really about the available active free chlorine as hypochlorous acid, HOCl. Based on the pool shop results, a FC of 12ppm and CyA of 130ppm will give you a FC percentage of around 8 which is sort of OK but questionable when the CyA is over 90ppm. I run at 10%. But those figures are just one moment in time, with a CyA of 130ppm and the industry telling you to keep your FC between 1 and 3ppm you have most certainly been running very low on HOCl over time which allows the algae grow.

The folks here at TFP are reluctant to offer advice based on strips or shop testing simply because history has shown these types of results to be inaccurate and advice based on them can cause more issues then they solve. Nothing beats self testing with a good kit.

 

[AUSpool]

I'm currently draining the pool to rebalance the CYA. How important is it that I add calcium once I replace the water? It's going to cost about $100 in calcium just to get it to about 400.

Mgtfp is on the money as usual, balance the CH as per your CSI. You will have about 90ppm calcium in the tap water. From there I would test and adjust. I wouldn’t go to 400ppm, if this rain ever stops the CH in the tap water will drive it up into the too high range. Use poolmath to calculate your CH, somewhere around 250-300ppm would be a good start. There is really no need to drive your pH down to 7.2. That’s the cause of your low carbonate alkalinity and will use a lot more acid. A pH of 7.6-7.8 would be much easier to balance. There is nothing wrong with a pH of 7.8 as long as the FC is kept at about 10% of your CyA. See the FC/CYA Levels

 

[Blew]

Geday Blew and welcome to TFP,

I have an older pool with ongoing tile issues too. I believe a lot of it is down to the adhesive and grout that was used. Ive used a product from Dunlop for underwater repairs but it’s messy, don't overwork it and don't expect an ‘as new’ finish. The Dunlop underwater adhesive will provide the the grout in one application. I would speak to someone in a tile shop with regards to adhesives and grout for above the waterline.

Browse Dunlop Tile All Plus - Dunlop Trade

Dunlop Trade's Tile All Plus product is a versatile tile adhesive that is suitable for various tile types. View now and get a reliable bond for your next project.

dunloptrade.com.au

Thanks a lot for this! It looks to be exactly what I need. Now to buy a diving belt...

Mgtfp is on the money as usual, balance the CH as per your CSI. You will have about 90ppm calcium in the tap water. From there I would test and adjust. I wouldn’t go to 400ppm, if this rain ever stops the CH in the tap water will drive it up into the too high range. Use poolmath to calculate your CH, somewhere around 250-300ppm would be a good start. There is really no need to drive your pH down to 7.2. That’s the cause of your low carbonate alkalinity and will use a lot more acid. A pH of 7.6-7.8 would be much easier to balance. There is nothing wrong with a pH of 7.8 as long as the FC is kept at about 10% of your CyA. See the FC/CYA Levels

Thanks. You make a good point about the calcium in tap water, which I'd assumed was 0 because I know that Sydney doesn't have "hard" water. I just had a look at the Sydney Water analysis (Prospect North delivery system) and am surprised to see how much calcium it does contain, despite being "soft", and even has some chlorine:

Total Hardness​

42 - 62 (mgCaCO3/L)​

This is a measure of the mineral content (particularly calcium and magnesium carbonates) of your water. Based on this result, your water is considered 'soft'.

Total Chlorine​

1.18 (mg/L)​

This is an average result for our measure of the effectiveness of the disinfection process we use to kill microbes that may cause disease. It also helps to make your water safe to drink all the way from our filtration plant to your tap.

pH​

7.74 - 8.02 (pH Units)​

 

[AUSpool]

Sorry, my mistake. My tap water tested at 75ppm CH, TA at 90ppm and pH 7.8. It can vary a bit but Australian tap water is fairly similar across the nation. Mg will normally be around 1/3-1/4 of the total hardness so it will be around 20ppm. At 75ppm CH my waters TH is a bit higher than the Sydney (prospect system) but is still in the upper limit of being considered soft water. The prospect TA at ~60ppm would break down to ~40ppm Ca and 20ppm Mg. The big takeaway though is that there is both CH and TA in our tap water.

And yes, there is chlorine. Mine tests at around 1ppm of FC. The total chlorine, TC, figure can include chloramine. I can’t remember the exact way it works but they normally guarantee a given concentration for the last house supplied where it can be a bit higher at the beginning of the supply system.