phosphonic acid

[PoolDoc]

Chem_Geek gave you the 'right' answer.

Here's a simpler one that's not quite so compliant with all the 'rules': HEDP is not very toxic, but is pretty acidic if concentrated. Still, if you just flush it, and then flush again after, there shouldn't be any problems.

But, I'd keep it. Just store it out of sunlight and out of severe heat, so the bottle won't deteriorate.

Ben

[rcy100]

What a viscious circle the pool stores have going.

Every opening/closing kit that I've seen where I live has - Oxidizer, 40% algaecide and "stain and scale" remover (which is the phosphonic acid). So you use this stuff at least twice a year (my pool store recommended algaecide and the stain and scale remover ONCE A MONTH), then they test for phosphates (which are increasing because of the phosphonic acid) and sell you phosphate remover.

[waterbear]

What a viscious circle the pool stores have going.

Every opening/closing kit that I've seen where I live has - Oxidizer, 40% algaecide and "stain and scale" remover (which is the phosphonic acid). So you use this stuff at least twice a year (my pool store recommended algaecide and the stain and scale remover ONCE A MONTH), then they test for phosphates (which are increasing because of the phosphonic acid) and sell you phosphate remover.

NOW you are catching on!