[QUOTE=waste]Grace, the problem is not the swg, but the salt itself. Any splashout on the exterior of the pool will contain salt. As the water evaporates and leaves the salt behind, the lethal (to metal) 6000 ppm can be reached and start rusting the walls.
I got the 6000 ppm bit and evaporation thing out of one (or more) of his posts on the old forum) Hopefully, this helps a bit, sorry I can't be more specific but maybe this post will spark the answers that I can't give - Waste
I would like to nip this notion of the "Lethal 6000 ppm" in the bud. I was the one in the old post that expressed my concern for above ground pools using a salt system. I explained that splash out or leaks would run down the side of the pool and get trapped in the bottom track of the pool where they would evaporate. This evaporation would create a concentrated salt residue, which would lead to corrosion issues. NEVER did I say that there was a magic threshold of 6000 ppm. IF 6000-ppm salt level caused that much trouble, there would be thousands of Watermaid pools around the world that would have died from this "Lethal" level. The reality is, Watermaid has used this level for 35 years and there is no "threshold" of corrosion or "lethal" level at 6000 ppm. The levels that I was talking about are those that we see on the sides of our cars in the winter (at least up here in Canada). A level more concentrated than ocean water and that IS a problem.
By increasing salt levels in a pool, you make the water more conductive. It is this increased conductivity that leads to corrosion. There is no magic level where the switch gets turned on and your pool rusts. It is simply an ever-increasing conductivity, which follows salt level. If we used distilled water and put absolutely nothing in it, the conductivity would be 0. If you add anything to it, it becomes more conductive. Dissolved solids increase conductivity. Where the big scare comes in is in the numbers that we use with pools. If we talk about 3000 ppm and then talk about 6000 ppm it seems like a huge difference. The reality is, 3000 ppm is 0.3% and 6000 ppm is 0.6%. One is slightly less than 1/2 of 1% and the other is slightly more than 1/2 of 1%. If you picture where these levels fit on a scale of 1 to 100 you begin to get a grasp of the true reality out there.
There are definitely some benefits as far as comfort goes by adding salt to a pool. The manufacturers decide where to draw the line as far as levels go and they all have heir own reasons for doing that. At the same time, we need to look ourselves in the mirror and decide whether our systems should be used in all situations. Watermaid has been clear from the beginning. Above ground pools present a situation that could lead to corrosion problems. That has NOTHING to do with the fact that Watermaid runs pools at 6000 ppm. It has everything to do with evaporation of ANY salt pool solution. WE do not make units for above ground pools and we do not plan to. There is a lot of money to be made in this market but we do have to live with ourselves.
Mark Manning
Watermaid Canada
www.watermaid.ca
mark@watermaid.ca
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