Quote Originally Posted by waterbear View Post
A few observations:
a 4.75 lb box of borax is $2.99 at walmart, target, and the local grocery store.
That's much lower than the what I found online. I'll have to check out the local stores next time I need some.

SWCGs do not cause staining. However, if you do not watch your pH and allow it to spike that can cause staining (and is usually what DOES precipitate stains.) If you know of two other people near you that have similar problems it is either the salt they are using (not very pure) or it's your water. Even city water can have iron in it.
I do keep a close watch on PH (test at least every other day if not everyday) and I don't let it get above 7.8. Could there be short spikes in between? Seems like if short undetected spikes are occuring, that the staining would suddenly appear, but it doesn't. It happens gradually over time. (Note; as I mentioned earlier, I've not had any staining since adding The Purple Stuff to my maintenance routine several seasons ago.)

I know 6 people in my area that have pools including myself (5 vinyl, 1 fiberglass). Out of the 6, 3 of us use the same SWCG system (we had our pools installed within a couple years of each other) and the other 3 use traditional chlorination methods. Those of us who use a SWCG have had metal staining issues and the others have not (we are all on the same city water supply). This in combination with the fact that staining doesn't occur when the system isn't running (ie - during the winter) leads me to believe there must be something to what I was told, that the SWCG separates out the impurities in the salt (which is what I suspect is the source of iron). It's also interesting that our iron staining issue followed the same pattern; 1st season no staining, 2nd season occasional staining, 3rd season staining more frequent, and so on. Perhaps I am missing or misunderstanding something?

While solar salt might take a bit longer to dissolve compared to a fine grained pool salt it tends to be very pure and rarely causes staining problems. I have seen 'pool salt' sit on a a pool floor and leave a stain behind. I have never seen solar salt do that. The fact that a pool salt has to include a stain fighter should tell you something. My suspicion that the 'natural stain fighter' is citric acid since that is was is often included in water softener pellets to 'clean' the units. Your expensive pool salt might be no more that ground up water softener pellets.
I have noticed that the label on the salt bags say they're 99.9% pure. Not sure if solar salt is more pure, or perhaps the pool salt has additives that aren't listed on the label? If the salt I currently have is using citric acid (ascorbic acid) then I'm fine with that. However, Ben mentioned it may contain "chitin (shrimp shell)" or "a mined ortho-phosphate" and seemed to suggest that I should avoid that. Perhaps I'll contact the manufacturer to see if they will tell me what they are using before I lug all that salt back to the store.

HEDP does not allow a filter to filter out the metals but this claim is often made. It chemically 'deactivates' the metal ions so they become non reactive for a while. The metal stays in the water until you either replace the water or it drops out of solution as a stain. If the stain is on a filter medium it is possible to change the medium and remove the metal.
The phosphates created by the breakdown of metal sequestrant are exactly the same ones that are 'algae food' but high phosphate levels do not mean you will have algae and are often NOT the limiting factor. Algae also need nitrate. However, there is no easy way to remove nitrate from pool water other than replacement of the water so a profit cannot be made by selling a product as it can with so called phosphate removers.
That's what I remember reading somewhere before. In season 2 (2005) when I was having problems with the liner getting slick frequently despite FC being around 7, my pool store tested for phosphates and found they were high. He said with high phosphates algae will grow despite good FC levels. Ever since then I use a phosphate remover in my closing routine that comes with the closing kit for mesh cover users. I use a solid cover now (MUCH easier spring cleaning!), but still get the mesh cover kit and apply the phosphate remover at closing as a precaution.

I would like to check my water to see if I still have metals and still need the sequestrant (I've been using The Purple Stuff for several years now), but according to Ben, it's seems sequestrants may interfere with the test results. So I guess the only way to find out if I still have metals (likely if the source is the salt as I suspect) is to stop using the sequestrant and see if staining returns. However, I really don't want to do that as getting rid of the stains is a royal pain and expense.

All this discussion has been very interesting and educational, although sometimes confusing to me. Lately I've been thinking about my current routine and how it might be made cheaper and easier, if possible. It has taken me some years to come up with my current routing which is working very well for my pool (no more staining or algae issues; pool always looks great), so I may come across as a little reluctant to change, and perhaps I am. Sorting though a mountain of information, and misinformation (!), has been challenging.

In the end it seems I'm down to two potential areas that might help me reduce costs and associated questions I need to answer;

1. Stain control. Can I safely stop using the Purple Stuff, or will I always need some sort of stain control (my suspicion is I will)? If I need stain control, is their a better/less expensive way? Would using different brand of salt help?
2. Algae control. Can I stop using polyquat and just rely on borates and chlorine? Looks like switching from "Optimizer" to 20 Mule Team Borax would net some savings.

It may turn out that my current routine is best for my pool and I should just stick with it.