Need help with white powdery residue

[Kecdvm]

Hi everyone,

I'm a new pool owner frustrated with this fine white residue on the walls/floor of our pool (the attached spa seems to be free of this problem somehow). When I brush the area the residue clouds a bit and moves some but never really goes away and the robot does not seem to be able to pick it up.

Here are the current numbers:
FC 7 (coming down from recent attempt to slam - before running out of reagent)
CC 0
pH 7
TA 70
CH 270
CYA 35

I have searched the site for similar problems and came up with these possibilities:
Calcium
Etched plaster
Algae

When we started out the FC and CYA were 0 and the CH was 0 (our city water registers with 0 CH)
The pool was neglected for year(s) and was green on day 1 (see last photo)

Pool plumber guy (who fixed multiple leaks) tried a muratic acid test along the wall on Friday and the residue came off so he suggested draining and acid wash.
Pool cleaner guy who vacuumed a bunch of debris and dead algae said he is clueless and did not offer any recommendations.

Since you can see a horizontal line where the old water line was I wonder if that means that it is damage to the pebbletec and the white cloud that comes off is plaster (I really hope not)

My next thought is to do the SLAM again (now that the larger reagent arrived) and follow by the mustard algae level for 24 hrs

Thank you for any advice!

Kristen

 

[pooldv]

Have a look at this and see if it helps to diagnose the problem, Diagnosing Pool Plaster Problems The white cloud could be scale or plaster.

If it is scale I would try a less aggressive approach before considering an acid wash. I would try taking your CSI down to -0.6 and brushing daily or as often as you can stand to. This could take weeks to solve it but an acid wash could notably shorten the life of the plaster, especially if there has already been etching.

Going forward maintaining CSI between -0.3 and +0.3 will prevent scale and etching and could add a decade to the life of your Pebbletec.

More here, Pool School - Calcium Scaling
And here, Langelier and Calcite Saturation Indices (LSI and CSI)

 

[Kecdvm]

Thank you for the recommendation. Could this still be calcium even though initially the CH was zero? I had to add a lot of calcium to bring it up to the current level of 270.

It also seems that despite the water being balanced (using pool math and CSI with my Taylor kit) in the last few weeks the overall 'whiteness' on the wall/floor surface is worsening.

I appreciate your help!

Kristen

 

[Richard320]

The powdery stuff could well be Calcium either from what you added or what's coming off the walls. It's highly possible that the previous owners were lax about startup procedures, too, and now you're paying the price.

True story: my water looked good but I kept getting white clouds every time I brushed for weeks and weeks. At times it was so bad that just standing on the top step to cool my toes left me with white feet, like I'd dipped them in chalk water. Brushing and vacuuming and maintaining the chemistry finally rid me of that stuff whatever it was. Judging by some other stuff that has come to light, my suspicion is that nobody brushed the pool after it was replastered and all the dust that normally gets shed in the first couple weeks just sort of hardened up and clung there until proper chemistry loosened it.

Get a wall whale brush and save your lower back. It provides the inwards pressure. All you do is move it up and down.