White chalky substance on pool walls/floor

[adam_d]

I know there are some threads already pertaining to this subject but couldn't find one that satisfied my situation so I'm asking on my own.

Levels as of tonight:

FC: 8 (this is currently on its way down from the SLAM I mention below)
CH: 200-225
TA: 90
CYA:35 (I know this on the low-end but the season is winding down and don't plan on swimming much more)

Brushed my pool the other day and noticed a thin white dust coming off the pool walls and floor. Note that I haven't been swimming much and I usually don't see this much during the middle of summer. Thought it may have been dead algae since I SLAMed a few days before but it keeps coming back within 24 hours or so.

Now I'm suspecting something to do with calcium, since I know I'm on the recommended low end.

My question is about calcium 'leaching'. Would this white dust be a symptom of it? I couldn't find anywhere that said leaching could result in a 'dust-like' form coming from walls, but it would make sense.

Plan is to bring up my calcium to 350 range to see if helps.

 

[domct203]

Your CSI is the important factor here for your plaster, what is it?

You also don't post pH, another important factor in the care of your pool surface.

 

[adam_d]

Forgot to put pH, knew I forgot something! It's about 7.4 now, although it was closer to 8.0 range at the time of the dust. I lowered it last night, will see if that had any impact on it tonight.

Interesting about CSI. I've been using this forum for a couple years and never come across it. Did a quick search and found that majority of users think if TA, pH and CH are in order, you usually don't have to worry about it.

I calculated it on PoolMath, and it said I was about -0.30 or so. I tweaked the CH value to where I plan on putting it and CSI changed to -0.16. I suppose 0 is the magic number.

I'm somewhat confident it's due to my levels of CH just need to be raised, but wanted to see if anybody had seen the dusty-walls scenario dealing with my kind of numbers.

 

[adam_d]

Brought my CH levels up to 300, and I continue to have a white powder coming off my walls and even more on the floor. I'm sure the stuff on the floor is a combination of dust and other things (I rarely vacuum) but I've been brushing the walls almost everyday for the past 5 days. I would expect those to be clean. It has to either be calcium or dead algae right? Fresh numbers as of 10 min ago.

pH: 7.3
CC: 0
FC: 10
CH: 300
TA: 60
CYA: 35

I also calculated my CSI with these and I'm at -0.44.

Somebody please provide some insight!

 

[pooldv]

How old is the plaster? CSI is a number that matters over the long term. Low or high CSI won't cause major problems in a month or two but it will over a longer term. If the CSI was below -0.6 or so over a period of many months or years then that could be the cause. If the CSI tended to run high, above 0.6 then there could be some scale build up and now that the CSI is negative it could be scale dissolving.

More about CSI here, Pool School - Calcium Scaling

 

[adam_d]

I'm unsure of the age of the plaster. I know it's at least 3 years old (when I bought the house), could be a few years older than that.

The past couple seasons, I believe my CSI would have been closer to the -0.6 range, due to not having my CH levels up, mixed with bottom-range pH.

I've since got those up to correct numbers and will maintain to see if conditions improve. Since changing my numbers, I'm guessing effects that CSI has on plaster aren't immediate and may take some time to take affect?

 

[JamesW]

It might be plaster dissolving or scale coming loose or paint or fiberglass chalking.

Sometimes gunite is resurfaced with paint or fiberglass.

Do you have a picture?

 

[adam_d]

I'll try to get some pictures tomorrow. I'm uncertain if the pool is painted white or if its plaster.

I have read that low TA mixed with low pH can cause some chalking. I usually try to keep my pH on the low end, and my TA has gone down over the season due to adding acid for high pH after it rains. I will get TA back up to recommended levels to see if it helps conditions.