They are either bluffing with the threat or are hoping that you will be scared off by the cost of defense. You should contact an attorney for the best approach. The following is just my opinion and obviously not legal advice.
As for your statements on your blog, all you have to do is point to scientific or other official references supporting those facts so I would just do that and send that back to them and welcome the humiliation they will receive in court (if they proceed) that will be done in a public forum (i.e. court proceedings are generally part of the public record) as well as a possible counter-suit you can file for a frivolous lawsuit (you likely won't win on that, however, since the bar for frivolous is ridiculously high) as well as bringing their attorneys to the professional conduct board of their bar association in their state for not doing proper due diligence (i.e. not being competent) and assisting a client in extortion (well, that's a stretch, so perhaps don't say that and you probably won't get a misconduct ruling in any event). You could also update your blog with these references (or others you find) as well. It only strengthens your argument.
-copper sulfate is ineffective at eliminating atmospheric contaminants and organic waste in swimming pool water;
As shown in
this link or
this link as well as in most any table of standard reduction potentials, copper ions are not strong oxidizers as the following half-reaction demonstrates
Cu
2+ + 2e
- ---> Cu(s) ..... E
0 = +0.337V
and its ranking among other substances shows that it falls well below ozone (+2.07V), chlorine (+1.36V; hypochlorous acid is +1.482V) and even dissolved oxygen (+1.23V) as well as non-chlorine shock which is
potassium monopersulfate (+1.85V), especially at the very low concentrations in pool water.
As for atmospheric contaminants, I'm not sure what you mean by that. Do you mean in terms of getting rid of disinfection by-products? I'd just avoid that statement as the more general one about copper not being an oxidizer takes care of its relative lack of reactivity with a large variety of common organic and inorganic compounds found in pools.
HOWEVER, unless they claimed that their copper sulfate was an oxidizer or didn't require use of any oxidizer (including chlorine), then you shouldn't be making your statement. It's not false, but it is misleading. You could change it to say that the copper isn't an oxidizer so still requires the use of an oxidizer to eliminate bather waste (i.e. it doesn't completely eliminate the need for chlorine for sanitation or for chlorine or non-chlorine shock for oxidation).
- algae is "good": it indicates something's wrong with the disinfection; it's not because pool water is crystal clear that it is automatically pathogen-free;
I would not say that algae is "good". It's unsightly and slippery so can lead to falls. It's not "good". It's just not unsanitary by itself -- that is, it is not a pathogen. It's also not good to use as an indicator for water quality since water may be unsanitary yet still not develop algae. I wouldn't use an argument of not using an algicide so that you can tell if water has gone bad. You should test the water for Free Chlorine (FC), not use algae as an indicator.
- the 0.6 ppm free chlorine these products suggest is not enough, especially in outdoor stabilized pools;
You won't be able to effectively argue this one. It takes a very low level of chlorine to kill most pathogens. Since the copper ion is killing algae, the water can be quite sanitary at 0.6 ppm. If the CYA level is too high, then this low FC level may result in slower oxidation, but that goes down the rat hole of trying to explain the chlorine/CYA relationship such as with this paper and
this one showing the slowdown of oxidation of ammonia and an organic (monochlorodimedone).
A low FC has the potential to "run out" locally under higher bather load, but this is unlikely in a residential pool. It may also be difficult to maintain that chlorine level since it will drop in sunlight, but again, hard to argue effectively especially if an automated dosing system or SWG is being used. The German DIN 19643 standard uses 0.3 to 0.6 ppm FC with no CYA, for example, though obviously automated dosing systems are involved in that case.
- use too much CuSO4 and you'll possibly get green hair and staining;
They may claim that their product contains sequestrants that prevent too much free copper ion from being in the water and therefore would prevent green hair or staining. They may also claim to limit the amount of copper in the water so that it won't stain. All you could argue here is the concentration of copper that can stain at various pH levels (forming copper oxide or copper hydroxide, etc.) or TA (forming copper carbonate) or CYA levels (copper cyanurate).
You can refer to the large variety of copper stain removers on the market, though again that doesn't prove that their product will stain. Many websites will talk about copper staining, but I'm not sure where you will find a definitive source that gives details about the levels of copper that can produce staining and then tie that back to the recommended levels for this particular product about which you are writing.
Perhaps linking to the hundreds of websites that talk about copper staining should be sufficient -- let these others do your arguing for you -- you are just a messenger and can say "may result in staining" as referred do in the following websites...
- if you really want to use an algicide, use a polyquat instead of a linear quat or copper sulfate;
Copper ions are a very effective algicide, even more effective than PolyQuat or virtually any other algicide suitable for pool use (except a sufficiently high FC/CYA ratio). So I would rephrase what you wrote by saying that if you want to avoid the possible side effects of copper sulfate, then consider using PolyQuat algicide instead. Quite frankly, if copper ions didn't have side effects, we'd probably recommend it so that people could have even lower chlorine levels in their residential pools (but of course it does have potential side effects so we use chlorine for algae control in addition to sanitation).
- as for the claims these products "stabilize the pH", my research shows that, if you follow the dosing instructions, the TA of a 10,000 liter pool will increase by 1 ppm, indicating that the CuSO4 is *probably* mixed with sodium bicarb; mixing the product with vinegar produces heavy foaming and gas, and you're left with blue crystals only. I'm not stating these products are cut with sodium bicarb, I'm just describing my findings.
You need to do more than just measure a TA difference. You should dose a large tub with a scaled down version of their product and note the pH change when adding an acid or a base. Then repeat with the same water without their product. This would demonstrate that the product has a negligible affect on pH buffering. Now as far as pH stability is concerned, that's harder to prove quickly since you'd have to show that their product didn't do something strange such as reduce carbon dioxide outgassing which would normally cause the pH to rise.
- CuSO4 is toxic for fish;
See the environmental data for
copper sulfate pentahydrate and
copper sulfate where it says the following:
The substance is very toxic to aquatic organisms. Bioaccumulation of this chemical may occur along the food chain, for example in fish. It is strongly advised that this substance does not enter the environment.
I would also look up their specific product in the
PAN (pesticide) Database. You can find
copper sulfate anhydrous,
copper sulfate pentahydrate and others where it lists "moderate to high" toxicity for fish.
You can also argue that copper ions persist while chlorine (which can also be toxic to fish) does not.
- Maintaining a pool is not expensive, neither copper, silver or any other metals shouldn't be in your pool water.
I think you meant "should" rather than "shouldn't". This is a blanket statement that is best avoided. It is better to simply state the facts of the pros and cons of using copper ions. It's perfectly fine for someone to use a copper product if they understand the risks. It is an EPA-approved algicide (not a disinfectant, however).
Now if the manufacturer did not disclose the risks of staining or the toxicity to fish, etc. then that could be intentional withholding of materially important information a consumer needs to know for a purchase decision (i.e. fraud), but virtually no manufacturer of copper ion or metal ionization systems does that. It doesn't make it right, but I don't think it's a fight you want to make as it would get rather costly. Many of these sorts of products simply claim to "use as directed" where the directions indicate specific dosages and usually say to keep the pH within a certain range -- the combination of which will avoid staining. So they are technically correct and are just leaving out the risk of what happens if the concentration rises (say, from adding more product in maintenance doses and not measuring with a good test kit) or if the pH, TA or CYA levels get too high.
Richard
The next morning the trout pond and the lake were a brilliant turquoise color. The trout pond and the lake were also full of dead trout - thousands of them. Not just the ones in the pond, but the escapees that had made it to the lake. We had to scoop up hundreds of pounds of dead fish. The whole park stank of fish for about a week. The paddles for the canoes were also stained a pretty turquoise color.