CH Levels Glass Mosaic Tile With Epoxy Grout?

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Hanstb

Hanstb

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Gold Supporter
Sep 20, 2018
72
Miami, FL
Dear TFP Braintrust,

I have read various threads pertaining to tile pools and CH levels, most recommend maintaining the same CH levels as those prescribed for plaster pools, in my specific case (SWCG) the allowable range would be 250ppm to 350ppm.

Our pool was constructed of steel reinforced concrete (pour in place 3500psi) and is covered in Vidrepur glass mosaic tile, the tile was set and grouted using 100% solids epoxy adhesive grout, so in effect there is no cementitious or plaster material in contact with the water. The pool was finished in 2012 and as such the materials have long since cured.

I would like to maintain the lowest CH level practicable without jeopardizing the pool's finish or water quality, our home draws water from a private well and is treated to <30 ppm CH, the water is also treated/filtered and free of metals. I have a full water analysis from our well (pre & post treatment), this is done annually by an accredited laboratory, however, in the interest of brevity, I will refrain from posting the full report, but I can answer most any question about both our well and our output water which meets city potable water standards (except for chlorine levels, which are 0.0, we use UV sterilization).

Our pool is described in my signature line, but I will add a few additional details in the event they are relevant to any advice one of the forums chemistry gurus might offer. My apologies if I am omitting something important, please ask , and I will try to answer any questions accurately.

Our spa has jets (12) with forced a air blower. (I believe foaming can be a consideration with low CH levels)

Pool Water Chemistry (TF-100)
FC - 3.5
CC - 0.0
pH - 7.4
TA - 90
CH - 200
CYA - 40
Average temperature 91F (Maintained year-round with heat pump)
Salt 3300

We are undergoing major back yard maintenance and some renovations, while the pool is not being modified in any significant way (new return fittings, spa jets, floor drain covers and skimmer parts is about it) we did drain the pool, so a fresh fill is on the horizon. I intend to implement the water chemistry values recommended here on TFP, but would prefer to leve the CH as low as practicable, I would rather avoid having to blend in raw well water or remineralize the pool water to increase CH if at all possible, or at least keep this to a minimum.

So, what say the experts, can I maintain a lower CH level in my situation, or is 250 as low as I can go?

Thank you in advance for any advice!

Best regards
 
jblizzle,

The CSI was -0.420 when the pool was drained. If I where to leave the CH at 20 (the house water CH), even at a pH of 8.0, that would yield a CSI of -0.830 which seems out of line.

Would pH 7.5, CH 150, with a CSI of -0.450 be acceptable, or am I misunderstanding the chemistry?
 
That is more negative than I would want to keep it.

I misunderstood and thought the pool water was now CH of 200ppm which is manageable, but 20ppm is just way too low.
 
You didn't misunderstand, the water was at 200 CH when we drained the pool, I will have to fill the pool with new water and was asking if I could target a lower CH or not?

The idea is to have the best possible water balance with the lowest possible CH as secondary, but desirable, condition.

Our well water is +/- 450 ppm CaCO3, so technically I can set the pool to whatever I want by blending well and softened water, I guess I am just leery of hard water.
 
On a related note, is blending the well water with treated water the best practice for attaining the desired CH, or would filling the pool with treated water at +/- 20 ppm CH and then adding calcium chloride be a better (albeit more costly) solution?
 
Depends on what all is in your well water I think. Are there metals? Does your softener remove them? If so, might be better to use all treated water and then add CH.
BUT ... this raises a question. Can your well pump and softener really keep up to completely fill your pool?
 
Yes, the water softener and the pre filters can handle the pool fill, that part of the system is capable of 50 gpm continuously, our RO on the other hand is far too small to fill the pool in a reasonable amount of time.

The pre-filters (ion exchange water softener and everything present before the RO) do not, to the best of my knowledge, remove any metals. The system consists of several cartridge filters down to 5 micron, a carbon filter, the softer itself, and a UV sterilizer. I have an irrigation line that bypasses the water softener and the UV light, this line is also only served by a 20 micron filter, this line is the other option for filling the pool.

As an FYI, the LevelSmart that maintains the pool water level is connected to an automated valve that uses treated water at 20 ppm CH.

The well water is nearly devoid of metals, the results this year were as follows (results in ppm, limits are those informed by the lab):

Aluminum 0.0
Arsenic 0.0
Barium 0.0327 (limit 0.70)
Cadmium 0.0
Coper 0.0182 (limit 2.00)
Chromium 0.0
Iron 0.0
Magnesium 0.0
Mercury 0.0001 (limit 0.001)
Lead 0.0
Sodium 114.5900 (limit 200)
Zinc 0.0136 (limit 5.00)

Unfortunately I do not have test results from after the pre-filters and softener and before the RO, the RO removes all of the above trace metals so the only other report I have shows these values at 0.0 (except Sodium), but I am nearly certain that's all the work of the RO and not the water softener.

If I had to guess, the only difference between well and treated water would be calcium (449ppm in my case), particulate matter between 20 and 5 micron, and UV sterilization, the latter seems mute since I will begin to add chlorine almost immediately once the pool begins to fill.

Does anything stand out as a potential problem, or should I just blend the well and treated water to achieve the 250ppm target CH?
 
Thank you for taking the time to reply to my posts, I must confess I was rather hoping for a "sure, with glass tile and epoxy you can run the CH as low as you like", alas I will adhere to the recommended values.

I made the mistake initially of treating my pool as a 'fire and forget' system, I foolishly relied on the automation to keep everything in check and thus failed miserably, the headaches that produced are still fresh in my mind, not the least of which was the calcium buildup on my tiles, and the acid wash required to remove it. That early experience left an indelible impression on me and I came to fear CH like the plague.

I realize now that scaling is a product of poor water chemistry and not absolute calcium content, I have made considerable improvements to my pool maintenance regimen in the past couple years, and now, armed with the knowledge gleaned from the the pages of TFP, I will make a clean go of it with fresh water, new filter elements, and renewed system components, wish me luck!

Thanks again for taking the time to reply.
 

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To be honest, I'm not sure if that epoxy grout would be impacted by low CH or not. Obviously the glass will be fine but I would rather be safe than sorry on your grout to deteriorating.
 
The epoxy grout has held up perfectly with the pool water at 200 pm/CaCO3 with a pH of 7.4 to 7.8 and TA of +/- 90, so I am reasonably confident 200 CH is ok. The problem in the past was if the TA/pH got wonky, aggressive scaling would occur very quickly. My desire to lower the CH was born of this concern, I felt soft water would provide a safeguard against scaling should the water chemistry inadvertently fall out of balance due to periods of inattention.

Why is a higher CH level specified for SWCG pools? Is it that the additional salinity contributes to the corrosive nature of water?

In any event, I will be making every effort to keep our pool properly maintained going forward, and make some adjustments to our water chemistry aligning it more closely to the TFP recommended values, particularly CYA and FC which have been managed at the much lower levels specified in the Pentair manuals. This will necessitate more frequent testing and more than likely also require abandoning ORP as a measure of sanitizer in the pool and isolating the SWCG from the Intellichem controller, there will undoubtably be a learning curve involved. I have been reasonably successful in managing pH/ORP/FC levels through automation, once I gave the system due attention, but if what I am reading on the forum proves accurate, maintaining the higher CYA/FC levels recommended here will exceed the capabilities of the ORP side of the Intellichem system.
 
A higher CH is recommended for swg pools because the added salt in the water lowers the CSI as well as the desire to keep the TA lower to slow the pH rise which also makes the CSI lower.

You can play with pool math and see how the various parameters impact the CSI calculation.
 
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