Crystal buildup on floor at opening

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Surf NH

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Jun 8, 2022
27
Hollis, NH
The pool service opened our pool yesterday, it's two years old gunite in New Hampshire, 39,000 gallon, UV/Ozone Chlorine system....cold and rainy, great timing ehh? The guys doing the opening said this was easy, chemically not far off, it looked really clean inside. They hooked everything back up, brushed the entire inside, all looks perfect. They also added half gallon muriatic acid, did a shock, and added something abbreviated as "accmo", not sure what that is.....alkalinity adjustment? I wasn't watching this.

Initial numbers they recorded for me before they added anything, ph 8+, alkalinity 70, chlorine 1.0, calcium hardness 300. I retested myself today as followup, ph 8.2+ (way off my scale), alkalinity now 100 (so maybe they did this adjustment), chlorine 5+ (makes sense with shock), calcium hardness 300. Water temp is 51F.

They hooked up the Polaris before they left....within an hour we looked in the pool, Polaris is on its side. Pulled it out, the bag was full of crystals....crystals so heavy the Polaris can't work. In fact, since yesterday we can only run the Polaris about 30minute before it fills up with crystals and is just dead in the water from heavy weight, we empty the bag and start again.....we've collected literally gallons of crystals in 24 hours. We've never seen this.....

I did a search on this forum, found a similar post from years ago.... Sediment/Crystals on pool bottom here are some pictures of our crystals. I'm thinking this unusually high ph is related somehow to what's going on, the water pulling calcium somehow from the plaster walls. At this point I'll continue to try to vacuum out the crystals while bringing down the ph. Any ideas out there on other actions?

One last point.....we found this article, seems to indicate these are calcite crystals, though I'm not sure what to do to deal with them? We did have a mesh cover over the pool for winter by the way. Calcium Crystals vs. Scale


IMG_1719.jpegIMG_1722.jpegIMG_1721.jpeg
 
I have never seen those crystals before but I will add that ANYTHING precipitating out of your pool water most always is caused by putting something in your water that didn't belong there.

That's not very helpful to your issue but is always a good reminder to leave the magic potions at the pool store
 

Sediment/Crystals on pool bottom

During the winter I noticed a lot of sediment on the bottom of the pool; it was deep enough in places so that when critters were squirming it would leave tracks. I'm in the process of opening and notice that my auto pool bottom cleaner (my 3yo calls it "the dude") if filling up with this white...
www.troublefreepool.com www.troublefreepool.com
 
JamesW said:

Sediment/Crystals on pool bottom

During the winter I noticed a lot of sediment on the bottom of the pool; it was deep enough in places so that when critters were squirming it would leave tracks. I'm in the process of opening and notice that my auto pool bottom cleaner (my 3yo calls it "the dude") if filling up with this white...
www.troublefreepool.com www.troublefreepool.com
Click to expand...
correct, I referenced the same link in my original post.....mine looks the same, though I'm not sure what they did in 2015 to get out of it.

Just for reference, I think it's some sort of crystallization that occurred during the cold water time in winter, with calcium somehow leaching out of the plaster. We've been running the Polaris for two days during daytime, emptying it every hour. It's most definitely collecting less crystals than two days ago, so seems I'm cleaning it up a bit. Will keep working to get the ph lower and see how things end up.

I've got a call into our pool maintenance company (same as did the install), and I stopped by the place I buy all my pool chemistry from locally.....they had never seen this before.
 
Put the crystals in vinegar, if they fizz then they are carbonate. If they do nothing but seem to very, very, very, imperceptibly dissolve, then it's calcium sulfate.

IF, you can take the crystals and put them in concentrated MA and they still do nothing, then it's calcium phosphate scale.

My guess, just based on appearance , is that it is sulfate scale.
 
JoyfulNoise said:
Put the crystals in vinegar, if they fizz then they are carbonate. If they do nothing but seem to very, very, very, imperceptibly dissolve, then it's calcium sulfate.

IF, you can take the crystals and put them in concentrated MA and they still do nothing, then it's calcium phosphate scale.

My guess, just based on appearance , is that it is sulfate scale.
Click to expand...
okay, making some progress....the crystals totally fizz in vinegar, dissolve within 20 to 30 seconds....so they're carbonate, ehh?....is that the same as calcite, and where would it come from, the plaster walls? Just an fyi, the calcium hardness was 400 to 450 in September before we closed the pool. Now it's 280 to 300.....could the calcium hardness reduction be related to the crystal formation?

Also, the polaris is hardly picking up anymore crystals from the bottom, seems they collected during winter and we've sucked them all up.
 

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Calcite is calcium carbonate. Calcium sulfate is gypsum. Calcium phosphate is sometimes called apatite but that usually requires an additional anion like hydroxide.

You likely had high calcium along with high carbonate alkalinity and high pH. That will cause the precipitation of calcium carbonate from the water onto the plaster surface. Luckily it all came off. Sometimes it can grow on the surface and adhere strongly making it difficult to remove.
 
JoyfulNoise said:
Calcite is calcium carbonate. Calcium sulfate is gypsum. Calcium phosphate is sometimes called apatite but that usually requires an additional anion like hydroxide.

You likely had high calcium along with high carbonate alkalinity and high pH. That will cause the precipitation of calcium carbonate from the water onto the plaster surface. Luckily it all came off. Sometimes it can grow on the surface and adhere strongly making it difficult to remove.
Click to expand...
so it seems we just even out the chemistry, we got the ph closer down to 7.6 now, and keep doing what we're doing. Water looks really clear, polaris is sucking up remaining crystals, and see if it happens again next year.

thanks for all the help, appreciated.
 
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