Sequestering Agent caused an enormous amount of white precipitate to pool

[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.