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Thread: Salt build up from bleach - flagstone problems?

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    Join Date
    Dec 2013
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    East Texas
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    Salt build up from bleach - flagstone problems?

    I have lots of flagstone in my build - flagstone coping and flagstone beach entry. Many people have talked about sealing flagstone with SWG pools due to problems with spalling/deterioration of the flagstone related to the high salt levels. I do not have a SWG and use TFP method with bleach, so I did not worry about applying a sealant to the flagstone. I started thinking recently about salt build up over time - my fill water is fairly salty at 600 ppm, and I know that bleach adds a bit of sodium over time. Does anyone know of a specific level at which sodium becomes a problem for flagstone? It seems plausible that within a few years I could be approaching SWG levels of sodium in my pool, and I'm wondering if I should consider a partial drain and refill at some point if the sodium levels get too high.
    30X40' free-form gunite/plaster pool, 4-8' deep with flagstone beach entry, gunite "rock" retaining wall with multiple small waterfalls/planters, grotto/slide/waterfall combo, 18" raised spa with waterfall into pool

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    Charlie_R's Avatar
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    Re: Salt build up from bleach - flagstone problems?

    I doubt you will have a problem anytime soon just from the bleach.

    According to pool math, using 25,000 gallons as an example, 100 oz of 8.25% bleach will raise your salt by only 4.4 ppm while giving you an FC rise of 2.7 ppm.

    Your fill water, however, may become troublesome. Is this from a water softener?

    I don't know at what point it would become problematic for your flagstone, but I'm sure someone else here might be able to shed some light on this.
    15'x48" 4500 gallon Intex pool, buried 1.5 ft. Pac-Fab Dynamo 3/4 hp pump. Hayward S180T sand filter, bought used. Taylor K-2006 test kit. Rocket mass heater based wood fired pool heater.

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    Re: Salt build up from bleach - flagstone problems?

    Unfortunately, not from a water softener (though I do have one for the house). I am on a rural community water service and the water is basically salty well water diluted with (more expensive) lake water they purchase from a nearby city. My 600 ppm of sodium seems like nothing compared to the 1000 ppm in my well water I use for irrigation. This is why I also have to be very careful with plants that I buy for my landscape. If it's not really drought tolerant or if we don't get a lot of rain, I will probably kill it with salty irrigation water. We have a small RO unit for the house for our drinking water, but it can't keep up with any high volume demands. Unfortunately, here in rural East Texas there are no pool RO services so I can't really consider that as an option for dealing with the salt increasing. Using pool math I calculate a 4.7 ppm daily rise at my current chlorine usage. I'm guessing (as I've not had experience with the pool over the winter months) that I could have anywhere from 800-1000 ppm increase in Na per year without accounting for splash out and rain. At that rate within 3 years I'm at SWG levels which are reportedly bad for flagstone. I doubt there is any actual scientific analysis of this regarding a specific Na level and flagstone damage, but I'm mainly interested to see if anyone has opinions or perhaps real-world experience with something like this.
    30X40' free-form gunite/plaster pool, 4-8' deep with flagstone beach entry, gunite "rock" retaining wall with multiple small waterfalls/planters, grotto/slide/waterfall combo, 18" raised spa with waterfall into pool

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    Charlie_R's Avatar
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    Re: Salt build up from bleach - flagstone problems?

    Check with Richard320 Ask him about rainwater catchment for your pool. It could be as simple as running all your downspouts into the pool, or at least into some sort of tank or barrel, that you can pump from into your pool, to do what you can to reduce the salt problem. That at least will buy you some time on the salt levels.

    Rural East Texas -- Sounds like the Midland/Odessa area, or further south. Lived for a while in Hobbs, NM area, so am a little familiar with the briny ground water. Has a lot to do with the salt domes over the oil/natural gas deposits.
    15'x48" 4500 gallon Intex pool, buried 1.5 ft. Pac-Fab Dynamo 3/4 hp pump. Hayward S180T sand filter, bought used. Taylor K-2006 test kit. Rocket mass heater based wood fired pool heater.

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