Sequestering Agent caused an enormous amount of white precipitate to pool

[BlueWaterMike]

Just joined the forum and this is my first post. Anyone every experience a major outbreak of a white precipitate form after using a sequestering agent? The precipitate is sitting on the bottom of the pool and I am running my Dolphin Robot as often as possible to clear it out. In the pool it is a powdery substance that clouds the water when stirred up. In the waste bag of the Dolphin it is a thick consistency like that of wallboard spackle.

some things to note about my pool:
about 38k gallons, gunite, white plaster
SWCG
opened 2006
original fill water was via a truck. Top off from my well, which runs through an industrial grade water softener... i.e. I really do not believe I am adding any iron from my fill.

[CarlD]

Is the material a soft yellow? If so, you may be confusing pollen with a precipitate. Our evergreens here in NJ put out a pollen exactly like you describe, but I usually only see it in the spring where it coats my skimmer socks like crazy--just like spackle. If I see anything the rest of the year it's whitish-grey.

I'm not the expert on sequestering agents, which should only be used when you are PROVEN to have excessive metals, but my understanding is they are supposed to dissolve and suspend the metals, not precipitate them out. Are you also using something like a flocculent agent?

[BlueWaterMike]

It's not pollen. It's as pure white as white gets. I live in jersey too. And no flocculent agent.

[BlueWaterMike]

Once I am given permission to post images I will show some photos of what was in the bag of the Dolphin after the precipitate settled to the bottom. In meantime I will provide a You Tube link to how it looked in the water. Keep in mind this video was after it had already cleared up a ton:

http://www.youtube.com/watch?v=0VcTsFXXeLo

[PoolDoc]

Your YouTube indicates that you used Alden Leeds product, "Conquest". According to various MSDS sheets, this has been, and still is, a product containing 60% HEDP. Since this is the normal production strength of HEDP, that's probably all that Conquest contains.

If you overdose with HEDP in waters with relatively high calcium levels, you can precipitate a calcium phosphonate colloid. But (a) this is uncommon, and (b) normally it won't settle, but will leave your pool cloudy forever. There may be some unique mixture of conditions in your pool that caused the calcium phosphonate to settle -- lucky you -- if that's actually what happened.

Bottom line: overdosing with HEDP is NOT a good idea. This is definitely not a product where, if a little is good, more is better.

[BlueWaterMike]

Wow. Thank you. This was the exact answer I was looking for. Plus I suspected it may have been some form of Calcium precipitating. But here's the thing. My Calcium was somewhere around 280-300 all summer. If this is indeed Calcium phosphonate precipitating and I am removing it via my Dolphin Robot, wouldn't my CH levels come down? Or maybe they will go up if some was in the form of scale on the surface and is now in the water. This is something that always confuses me. "Precipitate as embodied on surface" as opposed to "precipitate loose in the water".

My other theory was my Borax coming out of solution and precipitating. But I checked my Borates and they are 50 ppm. Same as before.

As for dosing. I used 2 full Qts. seems like a lot, but that is the initial dose for a 40k gallon pool.

One last thing. Can you permission me to post an attachment? I would like to send you a pic of the white gooey stuf in the Dolphin's bag. Thanks for the help.

[PoolDoc]

Keep in mind that I'm not sure what happened. Also, unless you dried and weighed the white goo, it's hard to say how much calcium was actually present. Most likely the goo was mostly water, quite possibly some of it bound chemically.

Send your picture to me at poolforum@gmail.com OR post it by using a link to Google Drive, Flickr, Webshots or something like that.

[BlueWaterMike]

Well, whatever happened, the pool is quite clean of it now. I just cleaned the Robot's bag again tonight. The white residue is getting less and less. And the pool chemistry is all spot on. Also been brushing a good amount, especially the steps where the Dolphin rarely gets to. Thanks Ben. Glad I found your site. Will send you some pics to that email. Mike

[PoolDoc]

Your pics:

[chem geek]

This paper talks about the precipitation of calcium phosphonate, specifically calcium with HEDP.