Gentlemen, Please allow me to make an observation coming from a fairly ignorant person who has lived most of her 48 years in snowy and mostly cold Michigan. The salt that we dump on our snowy icy roads from November to March eats up the under carriage of our cars,causing them to rust, even if they have been "rust proofed". That same salt and de icer we use, over the 15 years we've lived at this house has helped erode and roughend the surface of our concrete patio brick walk way. For my poor little pool we'll just be using the BBB's as we only get 4 months of swimming. But ask anyone that lives in a snow and ice belt if salt contributes to corrosion and they will laugh! I expect this is the same if you live in a place near the ocean. Either way rinsing after use, (just like washing the salt off the cars in the winter) would make sense too. Maybe others that have lived both snowy and ocean places would know.. JMHO Kimrst

Here in Houston there are actually several large builders that require customers installing salt to sign a disclaimer before they will install the systems. Personally I think it's an overreaction to some of the bad press.

What's the real problem? I'm sure material selection plays a big part but I'm convinced lack of maintenance is the biggest factor. I think these systems can cause a false sense of security about water balance, partially because of the way some companies sell them. They create a "set it and forget it" mentality that leads to horrible water balance. I see the same thing on the commercial side of the business all the time...many people just judge the pool on whether it's "blue" or not and don't worry about it until it goes green. This is very common with trichlor systems...

In the interest of full disclosure I don't sell salt systems (not because they're bad, just because it's not the business I'm in), but I have worked with them quite a bit. I consider myself salt agnostic. I tell people the facts as I see them and let them make their own decision.

I agree with that.
I have read most of this long thread! From my understanding people seems to be afraid whether the area around the pool will be damage or not, and materials in the pool. Maybe beacuse that's what this thread is about
The real concern for me though is how the rebars in the construction is affected with salt in the pool(longtime effect). I would love to hear aspects regarding that! If it's not to OT
Myself is brought up near by the sea in summertime. A sea wich contains twice as high salt concentration than a ordinary swg pool and I can't say that I have experienced so many negative aspects from that. Re painting the house more often that's a fact but I haven't seen any rust around windows and stuff like that.
Like where Kimrst live we also put a considelry amount of salt on our roads in the winter time. Actually you don't here many opinions regarding if that will affect the freshwater in the long run. This is something that have been around forever so i don't think a saltwater pool will be considerd to pollute the enviroment, not here anyway.

Normally a SWG pool has less than one tenth the concentration of salt that the ocean has.

It is not usually possible for salt to get to the rebar in the concrete. Salt from splash out may accumulate on the surface of the concrete, but unless there are significant cracks it doesn't migrate very far into the concrete.

[EDIT] (Sorry, I posted without seeing Jason's post so duplicate information here.) [END-EDIT]

Sea water is actually more than 10 times as salty as a typical SWG pool (about 35,000 ppm vs. 3000 ppm). However, the issue is not so much with cement (such as in sea walls) as with natural stone, particularly stone that absorbs water. It also isn't about constant exposure, but rather wetting and evaporation cycles since that concentrates the salt and dries it out which with some kinds of stone may result in salt recrystallization pressure that cracks the stone. Limestone may be one of the more susceptible materials, but it really depends on the specific stone since some quarried limestone is more solid and less absorbent than others. Sealing the stone can mitigate the problem.

Why would rebar be an issue? It is deep within concrete and presumably is not exposed to moisture.

Richard

Jason and Richard!
It was a bad comparison I've made. It has something to do with which sea you are refering to, right . What I wrote hold thruth for my situation. On the west coast of Sweden is it approx 2% salt concentration and on the east coast is it less than half of that concentration.
The swg equipment I have looked into recommend a salt concentration of "at least" 0,6%. So I wasn't so bad on it

People who have looked into my thread "concrete pool up north" knows that I'm a self taught DIY and not a professional builder and don't want to appear as anything but a DIY either. So take what I write with that in mind
I have done my homework pretty well before I started my little project I think! and with the knowledge i got from that study do I still think my concern is valid regarding rebars that can corrode.
Yes, the rebars should not be exposed to either moist or oxygen, both those things make the rebars to corrode. On the other hand do we know that building a watertight construction in concrete is a complicated thing to do. And to work on the supposition that the construction should remain stabel and tight troughout it's lifetime is maybe to hoping for to much. There are different regulations on how thick cast the rebars should be sourronded with depending on what fluid the container(pool) should keep. I don't have all the figures in mind, but in a watertight construction is the least thickness of the cast 40mm. If you're going to build a container that are supposed to stand against harsher fluids/enviroments than water the thickness of the cast must increase. Thicker cast=more protection!!
If you bare in mind the testimonies earlier from this thread that people who have seen basketballs baskets rust after a year in an enviroment of an swg pool and stainless steel that can't stand the water without corrode, my concerne about the rebars isn't that strange. Maybe not something that I lay sleepless about! But you can't overlook the fact that you are exposing the construction for a harsher exposure. And as I said before should result in different construction methods.
Also the concrete itself are different not only the bars. I paid twice the money for my concrete compaired to if I had bought a mix suitable for a house ground for example.

I'm going to clear my pool with a swg myself and have excluded stainless steel for the plastic for that reason. But I'm aware of the risk.
Remeber that concrete can stand tons of pressure but none stretch so it's of most importans that the rebar construction is demensioned to stand against the course of time.
This is just my two cents and goes for concrete and NOT genuite that I don't know anything about. But a reflection that I've made is that genuite looks as it haves much more pores to it and not as solid as regular concrete, maybe that's the reason for why you always plaster the surface with a cement based component before water fill. But that's just a reflection.

//Mats

I didn't mean to belittle the concern. It is a valid concern but something over a generally far longer period of time and usually with much harsher conditions than found in even an SWG pool. This link, for example, talks about the problem and some solutions for rusting rebar in concrete (there is also this link about some corrosion inhibitors). It should be noted that the problem is far worse (more common) in environments where salt is used on the roads so the concentration is far higher than in SWG pools even accounting for splash-out and evaporation -- the quantities are far different. Nevertheless, the concern is valid -- I just don't know how it's going to be easily quantified.

Richard

Thanks for the links Richard I will read them when I get the time.
When you are saying "generally far longer periods of time" what time frames are we talking about?
And also "much harsher conditions" Adding salt to poolwater makes the water more aggresive, no doubt! how much?? much enough for people who have had their stainless steel lamps/skimmers for years without problems in their ordinary chlorin pools. After switching to swg, problem occurs after a season. If you have a leak in your surface corrosion become much more of a concern for that reason. I have read many articles about constructions that are ruined beacuse of carelessly made reinforcements. Problem you can see much sooner than you think.
unfortunately there are all in swedish and wont be to much of interest for you I guess.

As I said this is nothing I lay sleepless about but it is absolutely an issue you should consider while you dimension your construction on the drawing table.

There are different grades of stainless steel. The lowest grades will corrode in swimming pool salt water, but the better grades will not (at least in the time frame of interest, say 50 years). Nearly everything made for swimming pools these days uses the better grades of stainless steel. Manufacturers have had to switch to the higher grades of stainless steel specifically because salt pools have become so common. Some older fixtures used the lower grades, so there is some risk when adding salt to older pools.

Most American SWG systems recommend salt levels around 3000 ppm. Australian SWG systems have tended to recommend levels around 6000 ppm. In Europe the recommended levels seem to vary more depending on the manufacturer. There are some corrosion issues that become much more significant around 5000 to 6000 ppm, notably some (not all) copper based heat exchange coils in pool heaters are at risk at the higher salt levels.

The corrosion risk for various materials depends on the salt level. The rate of corrosion varies with the salt level, but it isn't linear. Higher salt levels always have higher risks, but when you cross certain thresholds the corrosion risk can jump up very dramatically. Because of this, there is no straightforward way to estimate the corrosion risk at swimming pool salt levels based on studies using ocean water salt levels.

Concrete tends to be somewhat porous. Because of that most concrete pools are coated with plaster, which is very waterproof when properly applied. A concrete pool without a plaster coating will be at some risk of rebar corrosion with or without salt added, more risk with salt than without. A pool with a plaster coating has such a low risk of rebar corrosion that it isn't worth thinking about, other things will fail decades before there is any problem with the rebar.

Most modern SWG pools are 3000 ppm salt (the 0.6% or 6000 ppm that you quoted is for older SWG systems). Ocean water has around 35,000 ppm salt. De-icing salt on roads may fully saturate the water so be around 359,000 ppm. If the corrosion rate were linear, then failures of concrete structures for roads and bridges from de-icing salt after even 1 year would imply an SWG pool lasting more than 100 years. Obviously, there are other corrosive factors that would degrade a pool before this kind of corrosion -- again, assuming linear effects. We know that stainless steel corrosion is non-linear, but that's due to its passivity layer and the effect of chloride ions in disturbing its reformation. Regular steel corrosion is not like this so would be expected to have more of a linear effect based on conductivity of the water. There are many other factors including pH, presence of oxygen or other oxidizers, etc.

There's more about rebar corrosion in concrete here. If you do a search on "concrete rebar corrosion" you'll find many links.

Failures of plaster pools due to rebar corrosion in concrete is something I couldn't find anything about. Even non-SWG plaster pools typically have 500-1000 ppm salt in them yet they last a very long time and issues tend to be with calcium carbonate dissolving due to improper chemistry.

There's a long discussion about metal corrosion including stainless steel corrosion at The Pool Forum, but you can't access that since that site shut down overseas access. This PDF file goes into detail about the different kinds of stainless steel (as Jason discussed above) and the different kind of corrosion due to chloride ions and the passivity layer. Again, this is not the same as regular steel corrosion. There is no question that plain steel exposed to salty water will rust. This is true in a non-SWG pool as well. It not only has some conductivity from the intentional calcium and bicarbonate that are added for calcium carbonate saturation, but also has strong oxidizers, namely chlorine. This PDF file talks about how higher levels of salt lead to faster corrosion, but also how higher levels of oxidizer are a problem and how Cyanuric Acid (CYA) lowers the corrosion rate due to lowering the "active" chlorine (hypochlorous acid) level. This is consistent with reports we saw at The Pool Forum where some indoor SWG pools with no CYA showed fairly rapid corrosion of stainless steel within a year.

Richard

The corrosive effects of SWG water continues to be a topic with the manufacturers, too. While most aboveground pool manufacturers will void the wall warranty if SWG's are used, the steel wall manufacturers have not (vinyl liner "kits"). The negative effects of salt on travertine and other deck/coping materials also contiues to be a mildly contentious debate.

The enhanced potential for electrolysis (salt water being a better conductor), of stainless steel face rings, CPB face rings and ladders and rails (when aluminum anchors are used) has prompted two major manufacturers to offer a zinc "sacrificial anode" to be used. So far, the only major corrosion I've seen from my customers (dealers), has been with CPB face rings. We now tend to provide bronze anchors, rather than aluminum, to prevent the welding of rails to the anchors over time with SWG pools.

As stated in other threads, the various effects of weather, road salt, seaside air and such tend to present far more risk than do the SWG's.

Thanks alot for all the insightful answers. I'm really appreciate all the feedback !

My last thoughts on this subject!
First of all I'm not here to prove myself right or anybody wrong for that matter. My objective was just to raise the subject that concrete in enviroments that are aggersive can cause problems. Hence the many different materials bridge builders experiments nowadays in an attempt to get away from concrete in some positions.
In sweden has many projects started recently, projects that are trying to find other materials than concrete in bridges for example. Both wood bridges has been discussed/built aswell as plastic. This just beacuse there are so much trouble with reinforcements and the cost affiliated to that. Yes, those constructions are exposed to far harsher enviroments than our pools, but they are also built with totally different technologies than our pools, but still this isn't enough or it coast to much to maintain the concrete in such positions.
Again I'm pretty sure that the steps that I have taken in my project are enough to do the job and gonna give me long lasting pool hopeully. Especially with your words in mind. But what i mean is that we shouldn't take for granted that just beacuse you build your pool in concrete, that you are automatically free from problems. It's probably just the opposite, concrete demands greater ground preparations and dimensioning of the whole construction. Roughly speaking! You need to be careful in every step, not least reinforcements and casting thickness to get a successful result.

I browsed through one of the links Richard posted. I coulden't stop myself of posting this with following text: Conclusion

In conclusion, we have outlined corrosion protection methods to prevent steel rebar reinforcement in concrete bridges. Our nation of concrete highway builders need to wake-up to the fact that poor corrosion protection equal poor concrete bridge design and failure. Just like the following advertisement is trying to impress on us.

Regarding different stainless steels:
I don't know if you are familiar with Phaléns pool euquipments over here. Phaléns are for us the top of the line, swedish made quality steel(we are world famous for our steel qualitys as you all know ). I'm kidding a little bit, I can't tell what quality the steel actually are, but sold from them I assume it's not ****( I could find out what steelquality it actually is if you are interested).
A person installed their products in a pool similar to mine, stainless acidproof lamps and skimmers. Those has started to corrode after a season with swg. Phalens doesen't take responsibility for their stainless acidproof products if they are used in a swg pool. What everybody have told me is: If you're gonna use swg skip stainless steel for plastic. If I had known that I could use a certain manufactors stainless products i most certainly would. It's a pitty that I didn't became a member here earlier.


Finally!
Jason, I'm courious in what you wrote about plasters. I would like to investigate the possibilities to plaster my pool instead of my original thought, using an epoxy coating. What you said about its waterproof properties are very interesting. The problem is that I can't find anyway to buy such products. Do you know how I can get my hands on any of this plaster products? Have you heard of any brand shipping overseas. And do you think it's possible for a DIY project? I know there are a few stories on the net that describes the procedure, but I can't find them at the moment.

//Mats

Traditional swimming pool plaster is basically a mixture of white portland cement and marble dust. These days quartz dust, or a mixture of quartz dust and fine quartz sand, is sometimes substituted for some or all of the marble dust. An assortment of additives are often used to enhance various properties of the plaster, most commonly bonding and coloring agents. It is also possible to add various decorative elements, typically small pebbles, quartz crystals, or glass beads, for unique appearances.

Plaster surfaces require some care and more attention to chemical balance than epoxy surfaces. If treated well they can last several times longer than epoxy typically does.