Metal in pool

[waterbear]

Pool stain treat is just oxalic acid. It works exactly the same as ascorbic acid but is more toxic. (Citric acid also works the same.) You are just lucky the stain reformed in your filter and not in the pool. A sequestrant is still needed.

United chemical sell a lot of different products and makes a lot of claims for them. When you realize that the majority of their products are just soduim bromide (Pool stain Treat and the stain spotting bags being an exception since they are oxalic acid) and you look at the nonsense they call the Hamilton Index that they used to promote (and still do with their water balance recommendations) then you have to look at their claims for the products with a grain of salt.

I am not saying these products do not work, in fact they do (some better than others). It's just the marketing hype does not quite agree with the reality of what is really happening.