A sequesering agent is a chemical that binds with the metals that are in soluton (metals that lift off the surface of the pool after an ascorbic treatment, or metals that are in the water through other means). They usually say "helps control metals" on the bottle. Some of them are : Jack's Magic, Metal Magic, Metal Free, Sequasol, and many that are just brands that are sold at pool stores. Feel free to ask any other questions you may have
Thanks so much. I really don't know if it metal stain or not. it's a big dark spot comes and goes in the same spot. It really shows up more when my fc gets the high side. Any ideas? Oh...it's a vinyl pool.
Welcome to the forum. When you get a chance, delete your other post about this issue. I completely understand why you put it over there but keeping all your info in one thread usually gets you better responses.
Anyhow, what you're describing sounds like iron staining. A picture would help but the fact it seems to be more apparent with high FC sure points to metal. You say "dark" Dark Blue? Dark Green? Dark Brown? I'd say we can help you pin it down pretty quick with a pic or more description from you.
It sounds more and more like iron staining but, since I have no experience with that type staining, I would rather someone else get on board and coach you thru the process of identification and the solution.
Others will be along soon (almost surely today) who are really experts in identification and then keeping the stain out of your pool.
If it is Iron, it will respond to Ascorbic Acid almost instantly. Most vitamin C tablets are largely ascorbic acid. Take a Vitamine C pill and hold it on the stain for a few seconds (the longer the better) if your in the deep end it may take some rigging to hold it there unless you can hold your breath for a while and not float to the top. Whatever it takes, after the pill treatment you should see a visible change where you touched the stain with the pill. If you do not see any change --- it is probably something other than iron.
You can crush up a couple of vitamin C tablets and put them in a sock and rub it on the stain. You can also use ph down in a sock the same way. If it is a mineral (metals) stain it should lift up. Then you can try lowering the ph to 7.0 to 7.2 and using a sequestering agent - new stains will often lift off, but if they don't then you can do the ascorbic acid treatment. You can try rubbing a chlorine puck on the stain, if it lifts up it is an organic stain and can be lifted with high levels of chlorine over a period of time. Let us know how you do, and we can help you get rid of the stain
I've been dealing with a two different stains. The one is a large area that is light brown/yellow surrounding my drains that is mostly visible when it is cloudy. The other is a blue stain approximately 2 inches by 1 inch and is blue in color...blue looks like small pin-heads embedded in the plaster. I have tried ascorbic acid, but this didn't seem to work. I picked up a Jack's Magic Stain ID kit and found that their #2 (The Copper and Scale Stuff) worked. Unfortunately, I can not bypass my heater, which is a requirement for using this product as a stain solution. As a result, they recommend using Jack's Blue Stuff (1qt per 10,000gal - I have a 28,000 gal plaster pool) and then 1qt per week until stain is removed. Then go to maintenance levels (6-8oz per 10,000 gal). Here's my question, is Jack's Magic really any different from other liquid metal sequestrants?
Jack's Blue Stuff is basically the same as many of the other sequesterants. They do have some unique ingredients, which they don't list, but the primary active ingredients are the same as are in the others.