What causes calcium carbonate to pricipitate?

[dickeystorm]

I'm trying to understand if I'm doing something wrong. I get about 1/2 ounce or so of calcium carbonate in my polaris every 2-3 days. I tested it wit MA and it fizzles so I believe it to be CC. They are small white hard pieces. I can post a pic of a pile if it helps.

Todays readings
FC 4.5
CC 0
TA 90
CH 270
CYA 30
Temp 87F
pH 7.6
borates 15
salt 1400

Thoughts?

 

[zea3]

It sounds like you could have some efflorescence occurring in the pool. Your CH is not high, nor is your pH and TA high. When CH, pH, and TA are high you may form calcium scale, which might chip off in the Polaris, but I really doubt this is what is happening in your case.

 

[moyer02]

Undissolved salt? I had a couple of "white crystals" that were picked up a couple of days after adding..guess I didn't brush thoroughly.

 

[dickeystorm]

I'm not familiar with efflorescence, I'll have to read up on it. I do have some mottled coloring on the walls that I suspect is scaling but I'm not sure. I was going to take a pic tonight but got tied up, I'll post tomorrow.

I thought about salt but the only salt I've added is what's in the bleach and my number isn't very high. I also did the muriatic acid drops on the crystals and the fizzed, I don't think salt does that.

 

[JamesW]

If your plaster is old, it might be breaking down and coming loose. How old is it? What type of plaster? Is it plain white marblelite (calcium carbonate aggregate) type plaster? Your current CSI is a little low for plaster, and could be related if it's been low for a while.

 

[dickeystorm]

Here are a couple of pics showing what I'm getting. The pile of white stuff is from 2 or 3 emptyings of the polaris bag over a few days. Seems excessive to me.

I don't know how old the plaster is, I've only had the pool 4 years but the pool is 29 years old. As far as I know it is plain white plaster, no aggregate. The picture of the bottom shows a spot worn to the gunnite, there are several of them. The plaster is a little rough in places but looks fine in most. If you look close there is a discoloration on the plaster, kind of blotchy. Scaling?

Thanks

 

[duraleigh]

Well, your water looks very nice...good work!

That does not appear to be calcium scale to me nor does it appear to be efflorescence....neither comes off into your cleaner like that.

I think JamesW may have hit on the answer but he will have a better opinion than I after he sees the pic.

 

[JamesW]

Your plaster is probably white cement mixed with calcium carbonate aggregate. Most likely, the plaster is breaking down and coming loose. Raising your CSI to 0.0 might help slow it down, but it probably won't stop the deterioration. Try scratching the plaster with something to see if it is getting soft.

 

[dickeystorm]

Your plaster is probably white cement mixed with calcium carbonate aggregate. Most likely, the plaster is breaking down and coming loose. Raising your CSI to 0.0 might help slow it down, but it probably won't stop the deterioration. Try scratching the plaster with something to see if it is getting soft.

I was afraid of that. I don't really want to put a lot of money in the pool since there is a good chance we'll be moving in the not too distant future, 75 mile commute.

The plaster seems pretty hard to me but I don't really know what soft feels like. It definitely doesn't crumble to the touch. I have been able to drill into it fairly easy though while trying to figure out if I have a budding case of black algae. Small black spots in the plaster. Haven't been able to get one of the buggers out intake enough to do the smear test.

Looks like I should be investigating a replaster job.

Thanks for the help.

 

[JamesW]

As long as it's not causing you any problems, and you are OK with the appearance, then there is no urgent need for a replaster.

The roughness can harbor black algae, but that can usually be prevented by maintaining sufficient FC at all times, and brushing periodically.

You might notice some clouding when brushing due to plaster deterioration. If you don't have a SWG, then you could raise your CSI to about 0.0 to + 0.2 to help reduce plaster deterioration.

 

[dickeystorm]

I have noticed clouding when I brush. It settles back to the bottom fairly quick. Thanks for you input James