HEDP and stains

[Kim S]

I am a new pool owner (5-year-old pool came with house), and about 2 months ago I noticed faint brown stains on the sides and bottom. It's not bad, just not very nice looking. I bought the Jack's Magic Stain ID kit, and "Stain Solution #1" seemed to get the stain out just fine. The pool store guy said all I need is Metal Hold, which turns out to be HEDP. Since I read on a previous post that a small overdose of HEDP will precipitate unfilterable colloidal calcium phosphonate (and pool will look like milk to you drain it), I was hesitant to use this. But I am also hesitant to use the Jack's product, since I do not know what is in it; the MSDS was no help because it listed the components as a proprietary formulation. I don't want to add a lot of chemicals that could potentially make things worse. I have found your postings to be very helpful, thanks for any advice.

Pool Specifics:
IG gunite; 15,300 gallons; cartridge filter; no spa; Houston, TX
FC: 5ppm
TC: 5ppm
pH: 7.4
hardness: 230ppm
Alk: 105
CYA: 90 (I know this is high, have been working on filling and draining)
copper: 0
Iron: 0
TDS: 500

 

[mbar]

You can use regular ascorbic acid, it is basically what the stain solution 1 is. - and any other sequesterant you want. There are many on the market. I have used Jacks Magic the pink stuff, Metal Free, Metal Magic, Sequasol, and some others that I can't remember. They are all basically the same. If you want links to ascorbic acid I can post them for you. If you have the Jack's Magic stain solution 1 you can just use that and any other sequester you want. Feel free to ask any other questions you have

 

[Kim S]

Thanks. I have seen previous posts about ascorbic acid. So you think I need both ascorbic acid and the Metal Hold? Metal Hold bottle says "prevents and cures" stains, so I wasn't sure. I was more worried about Metal Hold (or any HEDP product) causing precipitates that could turn my blue water to milk!

 

[mbar]

The ascorbic acid will lift the stain off the pool - the sequestering agent will bind onto the metals holding them in suspension so that they do not fall out onto the surface of the pool. It depends on how much metals you have in the water - sometimes the sequestering agent will cloud the water - it shouldn't turn it into milk , however you should put enough sequestering agent in the water for the amount on the bottle, or a little more . Once there are metals in the water, they don't come out - just get suspended, so you will need to put in a metal out product in yearly, and depending on your water, sometimes as a weekly maintainence dose. One thing is it will be hard to balance the water again after the treatment. You will have to get your ph back up, and keep a close eye on the chlorine, because you can't shock for at least 2 weeks after the treatment. I just finished a treatment on my pool, and my water did not turn cloudy. I used proteams metal out for a sequestering agent. Let me know if you have any other questions

 

[Guest]

Please refer me to the post about HEDP precipitating out unfilterable calcium phosphnate. I have never heard of that and I am pretty savvy on water chemistry. Most of the seqesterants on the market are HEDP based ( or use one of the related phosphonates) or are EDTA bases (which are not as effective from my own experiences with them). The main disadvantage given ot phosphonate based seqesterants is that they will break down to orthophosphates. However, orthophoshates do not automatically lead to algae blooms as the makes of lanthenum based phosphate removers would like you to believe.

 

[Kim S]

Thanks, mbar and waterbear. The info about the HEDP precipitating out came from the old Pool Solutions tips web site:
http://www.poolsolutions.com/tips/tip40.html

Although I must admit I have not seen this info anywhere else, even in discussions of advanced pool water chemistry.

 

[Guest]

I respect Ben Powell's knowlege greatly but I will have to disagree with this. I regularly overdose 2 or 3 times with HEDP based sequesterants to help control staining in my fibeglass pool. In fact, Proteam suggests doing this with their Metal Magic which is HEDP to remove staining instead of using a stain remover like ascorbic acid. They have their 'sponge test' for stains and depending on how long it takes the stain to lift they recommend dosing 2 or 3 times above normal dosage. There is some temporary cloudiness of the water but it clears in a day or two.