Sand in filter. Is my plaster disintegrating?

[chuppi]

I run my pool robot once a week. I am seeing white sand particles. My plaster is the same color and I think it is my plaster disintegrating.
I check chlorine frequently and adjust. My PH is 7.4 which I check regularly and adjust as well. I don't check anything else. Please advice.

 

[jblizzle]

Well, why don't you check anything else?

If your CH and TA are low and you are keeping your pH that low, you could certainly be doing damage.

Do you have one of the recommended test kits?

How do you know what FC to maintain if you do not know your CYA? [FC/CYA][/FC/CYA]

 

[chuppi]

Sorry. I gave incomplete information in the beginning.
I did test CYA at the start the season and it was at 60. I know how much FC to maintain and I regularly check that. I usually check PH on a regular basis as well and it is at 7.4
Occasionally I check TA. It is currently at 110. I haven't checked CH.

I didn't have the robotic pool cleaner last year. So I don't know if I am seeing normal wear of the plaster or there is some problem brewing.

 

[JamesW]

Put some muriatic acid on the suspect granules to see if they bubble.

Bubbling would indicate calcium carbonate.

 

[chuppi]

Yes. it bubbled right away when I added the acid.

 

[JamesW]

Assuming that you have plain white marble aggregate, the plaster is probably deteriorating.

What's your total alkalinity and calcium hardness?

How old is the plaster?

 

[chuppi]

I bought this house just last year. I have no way to find out the age of the plaster. i have plain white plaster.
I know the TA to be 110. I don't have a test kit to measure calcium hardness. I didn't find one in TFTKit shop. I will soon do the test and post the results here. Thanks.

 

[JamesW]

Ok, your plaster is probably deteriorating. Keeping your CSI at near 0.0 is best for preserving whatever life is left.

TFTestkits.net

 

[chuppi]

Thanks James for your reply and time.
I didn't want to buy the full kit because I have everything else except for calcium hardness test. I have bought the reagents needed. I will post the CH in a few days.

I am hoping that I can get a few more years before re-plastering. I checked the forum on re-plastering and when to know it is time for re-plaster. It looks like it is hard to tell. Mainly if there are no leaks, it is okay to continue.

You asked me earlier to put acid on the residue and see if bubbles. It bubbled to indicate calcium carbonate. Is it possible that I have excessive hardness in the water and that is settling down?
Once I have the CH number, I will consult with you on keeping CSI near 0.

 

[JamesW]

Typically, if the particles look like sand, that's marble (ground calcium carbonate) aggregate from the plaster. Scale would usually not look similar.

Can you clean a small amount of the granules and take a close picture?

A clear picture of the plaster would also help.

Pool Plaster

What causes calcium carbonate to pricipitate?
In this post, you can see where the plaster near the main drain has worn away down to the gunite. It also had similar calcium carbonate aggregate coming loose.

Do you see any spots of gunite where the plaster has worn down?

Poolmix White Sand

Plain white plaster is a mix of white cement and ground calcium carbonate.

When the plaster cures, the cement contains calcium hydroxide, which becomes calcium carbonate.

If the CSI is too low, the calcium carbonate in the cement dissolves and the aggregate comes out.