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

[mshumack]

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

[gregugadawg]

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

[larry2338]

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'.

[waterbear]

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!

[sartail]

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.

[waterbear]

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.