Salt or Chlorine--info from builder has me scratching my head

[chem geek]

Sorry, but unless someone can show me some definitive proof that this problem is as widespread and dangerous as the PBs make it out to be, then my natural inclination is to just chalk their comments up to ignorance and a reluctance to learn something new.

See this post I wrote last month. This is not a new issue and has been discussed ad nauseam for years. The thread Saltwater Pools & Stone/Landscape Damage - It's the Weather? from 2007 was when we started to figure out why some areas of the country saw the problem much more than other areas. That's around the time I found papers describing salt recrystallization pressure and when we saw that in areas of the country with regular summer rains to dilute splash-out especially with high humidity that reduces evaporation (e.g. Florida) that didn't have issues while other areas that were much more dry in the summer and had low humidity (e.g. Texas, Arizona) had more issues and that this also correlated with the type of stone (i.e. softer stone used in Texas).

This is absolutely positively not some sort of made up problem. It is real. And because it is related to salt splash-out and evaporation, it happens faster at higher salt levels. It still happens in non-SWG pools but the effect is non-linear because if one is below the threshold where the splash-out builds up salt faster than it is removed, the problems will not be seen. Even when splash-out builds up, if it does so more slowly due to lower salt levels in non-SWG pools then it may take 2-3 times (or more) longer for the same damage to occur. Note that Australia doesn't see this problem (much) in spite of their 5000 ppm salt levels in their SWG pools (SWG systems were invented and first sold in Australia) because they are very used to high salt due to their ground salt levels and as such they simply don't build pools with features that are sensitive to salt (i.e. soft stone) and they use high-grade metal materials whenever possible.

Fortunately there are ways to mitigate the problem, most notably by sealing soft stone and concrete. Another technique is to frequently wash the splash-out areas.

Note that stone/concrete corrosion is not the only downside to SWG systems. Metal corrosion is another factor and again there are non-linear effects. If lower quality stainless steel (i.e. 304 instead of 316) is used or if aluminum is used (as with header bars that are sometimes immersed in "vanishing" electric safety covers), then these can get corroded. Having an aluminum over-track for a cover is particularly bad as shown in this post. Except for this latter splash-out issue, metal can be protected by using higher quality including cupro-nickel or titanium heat exchangers instead of copper and by electrically connecting a sacrificial zinc anode to the bonding wire and burying the anode in moist soil. See this post for some heater warranties and cupro-nickel claims relative to corrosion.

SWG pools have a lot of advantages, but to ignore their disadvantages and to not know when they work well nor how to mitigate possible issues is being biased, which of course is what many manufacturers of SWG systems did for years. Are Texas PBs going overboard by requiring riders or refusing installation of SWG systems? Yes, because if they simply took the care to design their pools appropriately for such systems, including explanation of required maintenance, then there wouldn't be so many problems.

 

[sbpse]

^^^^^The above should be a sticky somewhere. This comes up quite regularly and this is a VERY informative post on the dangers of SWCG and certain stone and environments. It is very good information.

Regarding them going overboard, I don't think they went overboard in the Austin area. Did they mark up the warranty, yes. But they didn't refuse and several of them tried to help steer toward more SWCG friendly choices (not sure if they were correct or not though).

 

[TexKSAH]

I've been wanting a swg for our future pool. I'd just about convinced hubby (even though EVERY builder tries to talk us out of it). The other night a builder really got into the topic and was very impressed with my limited knowledge of pool chemistry. I told him my concerns about trichlor tabs, cya levels, etc, and he attempted to allay my fears saying that a uv system combined with tabs and/or "dichlor" tabs would keep these problems at bay. He said eventually the cya in any pool even salt would be irreversibly high and require draining. I hadn't heard this before so I didn't have a rebuttal! What do yall think?


Sent from my iPhone using Tapatalk

Alliecat, we are in the Austin area and just started our pool. For almost a year now I have researched, learned, discussed and argued with PB's because I too wanted a SWCG. I am an engineer by trade and the PB we are currently using took the time to educate me and provide documentation and proof on how destructive salt water is to ANY product (concrete, plaster, grout, stone) that is made from the cement produced in Central Texas from the lime harvested in this area. I didn't like it, but I do understand it and would agree with your PB that SWCG is not advisable in the Central Texas area.

I heard some say "rinse your decks often", "seal the exposed concrete and rock often".... That may work for the exposed decking, but it will not help with the plaster/pebble sheen finish INSIDE your pool that is made with the cement produced from the lime mined in this area. Plus, doesn't that defeat the purpose of a TFP if your constantly having to do maintenance to protect your decking, rock finishes and your pool finish?

I am going with In-line Chlorine feeder and UV (UV-C wavelength produced by UV systems is many, many times more effective and more powerful inside the UV chamber than the UV-A wavelength produced by sunlight, so it is not totally worthless and will lower your total use of chlorine, but it cannot provide complete sanitation alone) and will be installing a stenner pump/liquid chlorine injector in the near future once the Trichlor pucks have my CYA up to the desired level. It is not the optimal situation that a SWCG would have been, but I have seen the proof of what salt does to any concrete or rock product from the local area after 3-5 years and I want to avoid that at all costs.

 

[chem geek]

I don't have an SWG yet annually seal our troweled concrete hardscape that simulates flagstone. There's no way we're going to even let weather damage ruin that surface given what we paid for it. Using natural stone or textured concrete requires maintenance. More maintenance in some situations than in others, but it is still required.

Unless you have an indoor pool, why are you getting a UV system? An outdoor pool exposed to sunlight breaks down enough chlorine to produce hydroxyl radicals throughout the pool and the bather load in residential pools is so low that you won't have any trouble keeping up using chlorine alone. So what is the point of UV?

 

[JoyfulNoise]

I heard some say "rinse your decks often", "seal the exposed concrete and rock often".... That may work for the exposed decking, but it will not help with the plaster/pebble sheen finish INSIDE your pool that is made with the cement produced from the lime mined in this area. Plus, doesn't that defeat the purpose of a TFP if your constantly having to do maintenance to protect your decking, rock finishes and your pool finish?

....It is not the optimal situation that a SWCG would have been, but I have seen the proof of what salt does to any concrete or rock product from the local area after 3-5 years and I want to avoid that at all costs.

I'd like to point out that the claim being made here by the PB that the plaster inside the pool will become defective or degrade due to salt water is specious at best. If it were true that salt in the pool water degraded plaster in that specific timeframe (3-5 years), then there would not be a single plaster pool built in all of Central Texas. All chlorine products, whether stabilized chlorine pucks, granular powder (trichlor or dichlor) or liquid chlorine bleach add salt to pool water over time as they all contain salt from their manufacturing processes. Annual use of 8.25% bleach in this specific pool size (100 gallons of bleach per year in 12,300 gal of pool water) will result in an annual accumulation of ~1,110ppm of salt. 100 gallons is a fairly conservative estimate based on a pool that is open all year long and does not undergo any periodic draining such as that found in winterization of pools on the East Coast. So in 3-5 years, the pool water will easily accumulate the same level of salt used in most SWCG systems (3,500ppm is the average, manufacturer recommended salt level for most SWCG's on the market).

If what your PB said was true, then everyone around you with a plaster pool surface using any kind of chlorine product would be seeing their pool surfaces falling apart. But look, I'm not trying to find fault with you specifically. If the PB made these claims to you and bases his warranty coverage on those claims, then no matter how illogical they are, you're stuck with accepting his terms or being denied warranty service. Generally speaking, this is the thing that bugs me most - PB's make these very general, vague claims about the damages done by salt with nothing more than anecdotal evidence and breathless scare tactics. Claims like these are typically easily refuted if enough information is available. I don't expect a prospective pool owner to start a fight with their PB over this and you have to do what they want you to do for the sake of the warranty coverage, but misinformation like this is very frustrating and only serves to limit the choices pool owners have.

 

[pabeader]

I use a UV 'filter' in my fish pond to kill the algae that sometimes turns it to pea soup. Wonder if that's what the PBs are trying to use it for?

 

[TexKSAH]

I don't have an SWG yet annually seal our troweled concrete hardscape that simulates flagstone. There's no way we're going to even let weather damage ruin that surface given what we paid for it. Using natural stone or textured concrete requires maintenance. More maintenance in some situations than in others, but it is still required.

Unless you have an indoor pool, why are you getting a UV system? An outdoor pool exposed to sunlight breaks down enough chlorine to produce hydroxyl radicals throughout the pool and the bather load in residential pools is so low that you won't have any trouble keeping up using chlorine alone. So what is the point of UV?

You are confusing UV-A (400nm wavelength/low power) sunlight with UV-C (200nm wavelength/high power) light produced by a short wave ultraviolet lamp. When passed through a quartz prism that filters out "trash light", the remaining UV-C is an extremely effect sanitizer that is used in laboratories, food processing, massive water disinfection plants and is mandatory on all commercial pools in many states. Plus, it does not deteriorate or hinder chlorine in any way. The bonus of UV-C is it kills everything chlorine kills plus some nasty things chlorine will not kill and allows you to keep a lower overall FC level in the pool as a residual sanitizer and is extremely cheap to install and maintain. The cost to operate it is cheaper than a 24W lightbulb that runs when your pump is running and will more than pay for itself by the reduced chlorine needed. I see zero downside to adding UV as an extra layer of protection that works with chlorine (not against it as sunlight does).

8 months ago I would have said "what the heck is UV-C?" lol

 

[skylar18]

I'd like to point out that the claim being made here by the PB that the plaster inside the pool will become defective or degrade due to salt water is specious at best. If it were true that salt in the pool water degraded plaster in that specific timeframe (3-5 years), then there would not be a single plaster pool built in all of Central Texas. All chlorine products, whether stabilized chlorine pucks, granular powder (trichlor or dichlor) or liquid chlorine bleach add salt to pool water over time as they all contain salt from their manufacturing processes. Annual use of 8.25% bleach in this specific pool size (100 gallons of bleach per year in 12,300 gal of pool water) will result in an annual accumulation of ~1,110ppm of salt. 100 gallons is a fairly conservative estimate based on a pool that is open all year long and does not undergo any periodic draining such as that found in winterization of pools on the East Coast. So in 3-5 years, the pool water will easily accumulate the same level of salt used in most SWCG systems (3,500ppm is the average, manufacturer recommended salt level for most SWCG's on the market).

Great point JoyfulNoise! I don't think people realize how much salt is in their non SWCG pool. When I did my original dump of salt into my new pool 30 days after it was filled, I was shocked to find out that I had already had 900 ppm of salt in my pool already... confirmed by my salt test and the SWCG itself! I had to yell at the PB to not throw in a bunch of bags of salt that he thought I needed.

That being said, I feel for the OP. There are so many stories, anecdotes, misinformation, true examples of destruction by salt or other reasons that it is impossible to have anyone say "This is the Right Answer. There are 6 pools on my little cul-de-sac. 4 are Salt, 2 aren't. 2 pools need their coping replaced. One pool was salt and one wasn't. None of them have needed their plaster replaced and most of their pools are 7-10 years old. Never heard of Salt impacting that. My buddy has a pool that is 10 years old south of Austin. His PebbleTec is ripped apart and they will have to replaster. Did not use a SWCG just liquid chlorine. I guess my point is I think it depends on numerous factors, including luck.

I personally love the how easy it is to maintain my pool and it only took me 1 hour to seal my stone this year. Went on an over 2 week vacation this year and came back to a perfectly clear pool. Could I have problems down the road? Maybe. All I can do is try to is minimize any effect of salt down the road, but realizing I might have the same issues even if I didn't have salt.

 

[chiefwej]

Texas pool builders love to use that soft flagstone and Texas limestone in their builds. It cheap, easy to work with and looks great. That is reason almost every pool builder in Texas tries to steer their clients away from salt pools. All natural stone is subject to damage and erosion due to salt exposure. It is more of problem in a climate with higher evaporation rates and infrequent rainfall. Softer more porous stone is much more likely to suffer damage than a harder type. Sealing the stone can delay, but will not stop the erosion of the stone.

My particular pool builder seemed acutely aware of this. When I expressed an interest in a salt pool he said: "Salt or stone, pick one, but you can't have both ". He designed my pool as a salt pool from the start. No stone anywhere, not even a coping. I have a cantilevered edge deck that is concrete with a textured vinyl overlay. There is really nothing exposed for the salt to damage. I have watched a neighbor's flagstone deck flake and erode away, due to exposure to his salt pool, so I know what salt can do to stone.

In the choice between salt and stone, I picked salt, and I'm glad I did. A well designed salt pool is a joy.

 

[TexKSAH]

Lol cheifwej, I know that choice but my wife had already picked out the peach flagstone for the coping and tanning deck and the white limestone (that matches our house) for the raised spa, firepit and water falls before we even talked with a PB. I never had the chance to make that choice!

 

[brebur]

For consideration I have a picture of how some of our coping has deteriorated since converting our pool to salt.

My pool was built in 1995 by the previous owner, and I purchased the house in 2000. We converted to salt in 2007. Up to that point, our limestone coping was smooth and had no blemishes, but starting a couple years later, we noticed sand in the pool and on our feet, and could see where some stones were a little rougher than others. The other day I examined all the coping to find good examples, and this photo is the best side-by-side contrast of the stone.

On the left, the stone is severely pitted, rough, and towards its bottom right corner, it has chipped/flaked off. The C shape hollow at the top is now about a 1/4" deep. The stone feels gritty, and appears less dense. You can rub your finger on it and rub grit off the stone, it's that soft.

On the other hand, the right stone is smooth, with sharp edges still (except for the chip lower left). This stone just feels denser, does not crumble, and is not shedding material.

It is not argued whether salt crystals can erode rock, they can. It's similar to how freezing water can erode rocks. Amazing natural structures like Utah's arches are made by this process. The real question is, will MY rock will be susceptible to it? Not all rock installed around a pool will be affected, but some might. And that's the risk PBs want to avoid.

FWIW, the salt concentration with our previous chlorinator was 4000+ (Zodiac LM3-24) for ~8 years. Current salt levels are 3800 for the new system (Circupool Si 45).

 

[chem geek]

You are confusing UV-A (400nm wavelength/low power) sunlight with UV-C (200nm wavelength/high power) light produced by a short wave ultraviolet lamp. When passed through a quartz prism that filters out "trash light", the remaining UV-C is an extremely effect sanitizer that is used in laboratories, food processing, massive water disinfection plants and is mandatory on all commercial pools in many states. Plus, it does not deteriorate or hinder chlorine in any way. The bonus of UV-C is it kills everything chlorine kills plus some nasty things chlorine will not kill and allows you to keep a lower overall FC level in the pool as a residual sanitizer and is extremely cheap to install and maintain. The cost to operate it is cheaper than a 24W lightbulb that runs when your pump is running and will more than pay for itself by the reduced chlorine needed. I see zero downside to adding UV as an extra layer of protection that works with chlorine (not against it as sunlight does).

8 months ago I would have said "what the heck is UV-C?" lol

I wasn't confusing the two. People who think about putting in ozone or UV into residential pools often do so because they believe it will act as supplemental oxidation and that's why I brought up the fact that the UV in sunlight breaks down chlorine into hydroxyl radicals that are very short-lived but powerful oxidizers so that for outdoor residential pools that are typically low bather-load, there is no need for supplemental oxidation.

UV-C absolutely positively degrades both hypochlorous acid and hypochlorite ion as shown in Figure 3 of the paper Photolysis of aqueous free chlorine species (HOCl and OCl^-) with 254 nm ultraviolet light where you can plainly see significant absorption in the 200-250 nm range though it is not as high as the absorption for hypochlorite ion in the 270-330 nm range (the UV in sunlight that reaches the ground starts at around 300 nm and up). The quantum yield is about 1 which means that the absorption results in breakdown of the molecule. So if you believed this baloney told to you that "it does not deteriorate or hinder chlorine in any way", then you should question the accuracy of the other claims you have heard. If you are not seeing any chlorine reduction from the UV, then the UV is extremely weak so what is the point in that case?

As for disinfection, it takes an incredibly small amount of chlorine to provide disinfection so the UV system will not let you use a lower chlorine level because the higher chlorine level maintained in pools isn't for disinfection (since a lower level would work for that) but for algae prevention. It takes a lot higher active chlorine level to prevent algae growth. While UV and ozone systems can kill algae that floats/circulates through their systems, they do nothing to any algae stuck on pool surfaces and the same is true for pathogens including bacteria as well. The main use for UV (and ozone) is in commercial/public pools to deal with the protozoan oocyst Cyrptosporidium parvum but that is not a pathogen blown into pools and would only enter your pool if someone with that pathogen with diarrhea had a release in your pool. Ozone is also useful for supplemental oxidation in such higher bather-load pools. However, in your 12,300 gallon pool, one person-hour of swimming only requires 0.086 ppm FC to oxidize the bather waste so obviously supplemental oxidation is not needed in most outdoor residential pools.

If you really just want to use a lower FC/CYA level, then you just need to use something to kill algae such as an algaecide like Polyquat 60 or use a phosphate remover. Then you can lower your FC/CYA level and still have decent (though obviously somewhat slower) disinfection and with an outdoor pool exposed to sunlight you'll still have enough for oxidation of bather waste that is minimal. So you could save perhaps half the amount of chlorine and it has absolutely nothing to do with the UV system. I had this argument with someone saying almost the exact same things you are saying (in this long thread on another forum), but for an ozone system, and after he did an experiment and found that algae was in fact not prevented in his pool with an ozonator when phosphates were higher, he conceded that his benefit of lower FC/CYA levels was not from the ozonator but from the phosphate remover he coincidentally used around the same time.

If you don't believe me, then throw in some fertilizer into your pool to get your phosphates above 1000 ppb, say to 3000 ppb like my pool used to have years ago and also add nitrates and then see what a bang-up job your UV system does to prevent algae growth at the lower FC/CYA levels you plan to use.

 

[bmoreswim]

That thread reference is the one I was thinking about. Love your informative 'summaries' of the facts Chem Geek.

 

[TexKSAH]

I was clear in my post and others where I get the response "if your pool is outdoors, UV is worthless" that I see zero downside to adding UV as a backup SANITIZER since it is cheap to install, virtually maintenance free and costs pennies a day to operate. And as you pointed out UV as a Sanitizer and "Outdoor pool" are not even part of the same conversation when you are discussing sanitization. Plus I like the idea that UV does it's sanitizing with absolutely no additives to the water.

I'm not going to try to discuss the article since I'm not that familiar with the concepts, but I will point out that the test/mesurements were done at a PH of 0-5, with a UV sanitizer 1000's of times more powerful than mine with extremely low FC levels. I'm not sure the findings are relevant to my pool vs the largest UV sanitizer in the world with FC levels below .5ppm at a PH of 0.

The PB we went with has built 4 pools in our neighborhood ranging from 2-8 yrs old. All with a UV sanitizer to supplement chlorine. I talked with them all and they all tell the exact same story... Pool water has never been anything but immaculate, maintenance consists of emptying the skimmers 3-4 times a month, cleaning the filter 1-2 times per year, testing a couple times a month and occasionally adding muriatic acid. None of them have ever had to shock their pool and have never had a algae issue. They all maintain their FC at 2-3 PPM and one (the only one regularly testing it) said his CYA has risen from 30 when installed to 50 now over a span of 4 years (very manageable rise). Whether its UV, auto fill, infloor cleaning system, chorinator, equipment or a combination of all of it, whatever the PB is doing seems to work and work well. All were very cheap to add except the infloor cleaning system so it was a no-brainer and as I have stated many times, a stenner pump down the road to replace the chlorinator if and when CYA becomes a problem is the plan.

I'm happy with my decisions and besides, it's too late. The equipment is installed and the gunite was shot in Friday!

 

[Marlahoutex]

So Allie, are you going SWCG? Inquiring minds want to know!!

 

[pabeader]

i wonder how many times the 8 year old pool has had to drain and fill?

 

[alliecat]

We are meeting with one of our top 2 tonight. My husband is very much wanting hassle free/standard/no frills/mainstream sanitizing and he thinks trichlor pucks like everyone does is the answer :-/. These pb's have gotten to him with their scare tactics and he doesn't want a waiver on a coping warranty due to possible swcg corrosion.


Sent from my iPhone using Tapatalk

 

[TexKSAH]

None of them said they ever have had to drain, but I didn't ask that question. Only one was monitoring CYA and if the levels progress the same, he will have to do a partial drain/refill in a couple more years. He was grateful to learn about the stenner pump/liquid chlorine idea and will most likely install one.

Still, one could argue that a partial drain/refill every 4-5 years is not a bad idea anyway due to salt and other TDS in the pool if you are not getting adequate replacement from evaporation/splash-out/discharge.

 

[JoyfulNoise]

We are meeting with one of our top 2 tonight. My husband is very much wanting hassle free/standard/no frills/mainstream sanitizing and he thinks trichlor pucks like everyone does is the answer :-/. These pb's have gotten to him with their scare tactics and he doesn't want a waiver on a coping warranty due to possible swcg corrosion.


Sent from my iPhone using Tapatalk

alliecat,

The point of TFP is not to steer anyone to a particular product. The TFPC Method is simple - understanding exactly what your pool needs, understanding what different chemicals do to your pool water and only adding those chemicals that meet the need and are proven to work.

So, at the end of the day, you can go right ahead and use trichlor pucks in an inline chlorinator. But, in order to use them effectively and maintain clear, sanitary water, you're going to have to keep a close watch on your stabilizer level and drain & refill water as needed to keep the stabilizer in check. TFP stresses the use of bleach or SWGs because they are the things that keep chlorine in the water and have the least side effects.

As for salt versus traditional pool, that choice is entirely yours to make and, if the PBs won't warranty any stone work with a salt pool, then you have to go with what they do offer. The point of owning a pool is to have something you and your family can enjoy without turning yourselves inside out or putting yourselves in the poor house trying to maintain. So do what makes you both happiest and everyone here at TFP will be happy to help you if problems pop up.

Oh, and if he hasn't already done so, see if your husband would be willing to read the info in PoolSchool. Not to change his mind, just to show him that his goals of pool ownership are exactly the same as all of ours - a trouble free pool!


Sent from my iPhone using Tapatalk

 

[sbpse]

We have also talked to pool owners in the area that use pucks and haven't drained in 4 years they have been maintaining them in that way. They seem to be doing fine with that setup. At least one was also testing CYA and said they didn't have enough rise in that 4 years to be concerned with switching methods. I didn't ask him his measured values though.

I suppose it could have to do with how much rain we get in a given year?