White powder accumulating on bottom of pool

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K

kwlis

Member
Jun 10, 2017
10
Richmond, TX
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
I watched white powder buildup on the bottom for the past two years, and finally gave in and vacuumed it out today. I would appreciate some ideas on measures that I can take to prevent more white powder buildup.

A few observations that might be worth reflecting on:
(1) Over the life of this pool, I am constantly fighting high pH. I chalk this up to fill-water chemistry. I add muriatic acid to push down to 7.5'ish, and then in 7-10 days (if we've had no rain) it's back up to 8.0'ish.
(2) I get some scaling on the leading- and trailing-edges of the SWG. It's never been so significant that I bother to ever clean it. Maybe I should be?
(3) When my IC40 failed - I replaced it with an IC60. I did this because my IC40@100% could barely keep up without running the pump for 20-hours in the summer. This powder-accumulation really accelerated once I upgraded to the IC60.

My most recent test results using my test kit:
  • FC 5.5
  • pH 7.8
  • TA 80
  • CH 575
  • CYA 80
  • Salt 2900
  • Temp 91F
  • CSI 0.27 (calculated by PoolMathApp)

Thanks!
 
I did such an effective job of vacuuming yesterday, that there’s not an accumulation of powder anywhere, to catch a sample of the powder (using the turkey baster). I was not accumulating more powder whilst I turned down my Chlorinator this past offseason, so I thought it was a foregone conclusion that this was Calcium in the first place. But I fully understand the recommendation to validate that it is Calcium, and will do so once I can see enough of it to capture the sample.

In the meantime, I will start suppressing the TA by MA dosing.
 
If you suspect scale lower your TA. Try to get it down to 60ppm. Maintain CSI in the negative range, closer to -0.30.

www.troublefreepool.com

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.
www.troublefreepool.com www.troublefreepool.com
 
@Rancho Cost-a-Lotta and @mknauss - Thank you both for the inputs. Over the course of this week I walked the TA down to 50 through numerous MA-doses. My most recent pH is 7.5, and CSI is -0.36. The white precipitates have completely subsided, I cannot find any at all to sample, so that’s good.

Out of curiosity I checked my fill water and it has TA of 150. Reflecting on the past many months, in Houston area we’ve have excruciating heat and no rain. I’ve never really monitored TA or CSI this year, but with the combination of higher water temps (+3F) compared to prior years, and higher-dependency on fill-water from the city, I believe the TA+CSI mismanagement was the root cause.

Will repost if anything changes, but I’m a happy customer. Thanks.
 
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