White Powder at bottom of pool showed up over night

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mrbookmanlibrarycop

Well-known member
Aug 30, 2019
94
Westchester, NY
Pool Size
22000
Surface
Plaster
Chlorine
Liquid Chlorine
I saw this white powdery substance at the bottom of the pool as i was getting ready to brush, it was not there last night when i was doing an OCLT test. It disappears & puffs up instantly when the brush hits it. I am trying to figure out what it is, two items I did yesterday may have something to do with it, but first, current test results (water is clear and passed OCLT test) :
FC: 7.5
CC: 0
PH: 7.8
TA: 60
CH: 300
CYA: 70

So, the two items are,
  • Was fighting an extremely high PH when i opened this Sunday, the test was showing higher than an 8 for sure, ended up using a decent amount of 31.45% to bring it down just to 7.8 (bought a new gallon from my previous thread :laughblue: ). As i was testing this, TA went down from 70 as I think that is expected, but CH also decreased from a 340 opening to 300 now.Would lowering PH from probably around 9 to 7.8 cause CH to decrease, and that could just be calcium deposits
  • Backwashed DE filter yesterday afternoon and added 80% DE back. My PSI is back to the normal operating range, and I did not notice any DE come out of the jets as i was pouring in.

As i brushed it all, i didn't vaccuum it up, if it settles again i will try and do that with a skimmer sock and see if it goes away.
But either way, any ideas what it could be? Calcium? DE powder? I didn't have an algae problem or perform any SLAM this year thankfully, but maybe could be just dead algae?
 

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Do you have a main drain plumbed to the skimmer? On a couple of occasions, I added DE to the skimmer without the float/diverter valve in the skimmer. The DE, sank down into the main drain line and ended up in the deep end. After a couple times of doing this, I realized what happened. I vacuumed it up and it didn't return.
 
Rancho Cost-a-Lotta said:
Do you have a main drain plumbed to the skimmer? On a couple of occasions, I added DE to the skimmer without the float/diverter valve in the skimmer. The DE, sank down into the main drain line and ended up in the deep end. After a couple times of doing this, I realized what happened. I vacuumed it up and it didn't return.
Click to expand...
My main drain is plugged actually, so it is not in use. Some of this powder i saw in shallow end too, pretty much in line with the return jet actually, so could be excess DE that escaped the filter, but just odd it would take atleast 5+ hours to show
 
Adding too much DE or adding the slurry too quickly can send DE to the returns. I don't have a multi-valve or backwash valve, but make sure your valve is positioned properly. I think you can rule out dead algae based on your chemistry and OCLT. Your chemistry doesn't hint at any issues with calcium. Calcium would likely appear more crystal-like and/or flakey. If you could capture some and drop MA on it, it would fizzle.

BTW, the Library Cop episode is one of my faves. I still watch Seinfeld every night. I keep hoping to see an episode I've seen before.
 
Makes sense regarding the DE, did go a little fast so very well could be it. I'm going out again in about an hour so hopefully the brushing disturbed it enough to not fall to the ground, otherwise i'll try to vaccuum it up. Appreciate the help!

The Bookman rant in Jerry's apartment is my go-to video to watch whenever i need a laugh.
 
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Hey All,

So went to brush/vacuum pool again and noticed those same spots yesterday and this AM. I was able to catch them in my skimmer sock as i am vaccuuming, turns out it isn't powdery but they look like small, round, ball-type substance. It isn't really brittle. Doesn't look like DE at all & I was able to put some in a drop of muriatic acid and it reacted pretty violently and fizzled out.

So, could that be calcium that is reacting to the basically gallon of MA i had to drop in the water to get it down to (now) 7.6? It could correlate with my CH dropping too? Is calcium deposits little balls like that? I do have some scaling so maybe that is dissolving, ill have to start taking pics of an area see if it decreases.

Any thoughts or anyone see those before? Will i just hvae to vacuum them out as they fall?

Maybe it's salt in the water? I don't have SWG and never put salt in before in the 10 months that I've lived here
 

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mrbookmanlibrarycop said:
turns out it isn't powdery but they look like small, round, ball-type substance. It isn't really brittle. Doesn't look like DE at all & I was able to put some in a drop of muriatic acid and it reacted pretty violently and fizzled out.
Click to expand...

Sounds like calcium. Can you post your most recent test results.

Here's a little bump for some expert advice :bump:

Maybe @mknauss @JoyfulNoise can help...
 
Fresh set

FC: 7
CC: 0
PH: 7.8
TA: 60
CH: 300
CYA: 80

No real change from the OP reading which seems good, hoping ph can be stable there after the MA dump

Thinking it's calcium too but the way it looks is strange, though idk if that is normally the way it looks.

But like I said earlier, when decreasing the ph from about 9 down to the 7s, CH went from 340 to 300
 

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The lower CH test is most likely testing variation. Adding acid does not change the level of CH tested.

Vacuum up the material. If it did not adhere to the gunite, call yourself lucky.
 
mknauss said:
The lower CH test is most likely testing variation. Adding acid does not change the level of CH tested.

Vacuum up the material. If it did not adhere to the gunite, call yourself lucky.
Click to expand...
Good to know re: acid and CH

Thanks! Hopefully I won't see anymore or atleast see less of it in the next days. Will continue to vacuum it out. Curious though, consider me lucky just that it isn't starting to scale?

Just strange how it just showed up.

Will update if I keep seeing this as an ongoing issue

Thanks all
 
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