Where do I buy Phoshonic Acid - and do I need it?

I am testing my water myself with Ben's test kit. I recently decided to have a pool store do a test for comaprison. The pool store suggested I add Jack's Magic ("Purple" for salt pools). I know they want to sell me something but I may be in agreement with them on this. The product claims to prevent stains - which I am concerned about because I top off the pool with high-iron well water.

Should I use a stain prevenative? I already have two small brownish stains near the main drains I can't get rid of. Jack's Magic says it contains Phosphonic Acid. If so, where can I get this stuff without paying $18 a quart? My pool needs two quarts per application.

I have a 20,000 gallon in-ground gunite pool with Diamond Brite type finish.

Thanks,
Mike

quit being cheap, otherwise you are gonna be spending 5000 for a new finish on that pool.

Don't know anything about Jack's Magic, phosphonic/phosphoric acid and certainly can't recommend for or against using any of the above. However, a quick search shows phosphoric acid available @ Lowes and Home Depot for ~ $7.00/qt.
IF...big IF... you can accomplish the same thing for 40 percent less money, I (not being a Retail Pool Store Manager) would not consider you 'cheap'.

phosphoNic acid is not the same as phosphoRic acid! Most seqesterants are based on derivatives of phosphoNic acid. If you are putting in water with a high iron content then a sequestering agent is a good idea. The Purple stuff is a decent product as is Proteam's Metal Magic. There are others equally as good. If you are not having a stain problem then all you probably need is a maintenance dose of the product and not the full treatment amount. Since you already have some iron staining in the pool you might want to do a full treatment and then treat with Ascorbic acid (this or oxalic acid is what the majority of stain removal products are; ascorbic acid is much less toxic.) Send a PM to Mbar for details, she is pretty much the forums expert on stains in pools from what I have seen!

Are there any "side effects" (like change in pH, etc.) from adding Metal Magic or similar products? I have a new pool and will be topping off with iron rich well water. I'm wondering if it is a good idea to start using a product like this to prevent stains.

usually yes but small ones. The ones I have used have always lowered my pH. Nothing a bit of borax can't fix! Some products want your pH or other paramters in a certain range before you use them. Just follow the directions and you should be ok. If you KNOW there is iron in your water they are a MUST if you don't want stains in your pool.

Hello,

Luke the semi-professional pool guy here. As regards to Jack's Magic, I do use their products regularly for stain removal. The purple stuff is correct for salt water pools. Blue stuff for chlorine pools. The stuff does work. But once you are on the product, you have to continue using it to keep the stains away. Most of my clients spend about $300-$400 for stain removal than $40 or so a month keeping the stain away.

Jack's Magic is the best in stain removal technologies. I love them, expensive, but good.

Luke

ps... jack's stain products will lower the ph, but not purple or blue stuff.