Plaster granules!

[shoot-straight]

Opened pool (company) 2 weeks ago. All was fine, did my best to maintain some FC and pH over the winter. It's a one year old concrete/plaster pool. Last year had no issues other than pH drift up, which I read was due to new plaster and SWG. Would add a bit of acid regularly, and it would go down.

On opening, all that was needed was some water and salt.

Pulled my polaris the other day and saw some granular stuff in the bag. I thought it was salt that hadn't dissolved. Pulled it again, and found out that it's not salt. Feels like fine sand. Clearish white in color. I felt the sides of my pool and they feel like sandpaper, but it brushs off pretty easily. its all over- not just in one spot. Opener didn't notice it and neither did I at the time.

The granules are way too uniform to be scale in my rookie opinion, each seems to be perfectly sized. Chemistry is good- CH 290, pH 7.5, CYA 40, FC 5, TA 90. Same numbers I ran with last year and had no issues. I am guessing it's from over the winter, it doesn't seem to be high on the sides, below where the water level was seems more affected.

i think my plaster is dissolving( or dissolved), but why? Again, can't be low pH or CH issues? Unless I had one over the winter without knowing. But I checked it pretty regularly. At least once a month.

thanks

 

[JamesW]

Might be scale. What was your ph at opening?

Based on the available information, I would suspect that the ph was very high at opening.

Try a drop of acid on the granuals to see if it bubbles. If bubbles, it's probably calcium carbonate.

What plaster did you get?

 

[shoot-straight]

Ph at opening was 7.8. Added 1/2 gallon of acid.

its just a white plaster pool.

pool builder says its sand that's blown in the pool-

Just did the acid test, it dissolved immediately.....

the regular brush doesn't do a great job getting it off, but my wire brush does good.

 

[JamesW]

It's not sand. It's either scale or marble aggregate from the plaster.

Fast dissolving is more likely to be scale.

Did you measure the ph at opening?

 

[Patrick_B]

JamesW is right, and this is most certainly not sand blown into the pool.

 

[JamesW]

I suspect that the ph was very high at opening. The report of 7.8 ph at opening is, in my opinion, probably an error in testing.

With relatively new plaster and 90 TA, the ph would normally be very high unless managed over the winter.

 

[shoot-straight]

James- it was indeed 7.8 at opening. I was adding acid and bleach monthly during the winter. I guess I needed to do it more frequently. I put in a bunch of chlorine and a gallon of acid about 2-3 weeks before opening.

Now I have to do two things.
1. Convince my pool builder that it's scale since I don't want to do anything aggressive to my still warrantied pool and plaster without his ok. He is still saying its blown in sand that glues itself to the plaster....

2. Find the best and least aggressive way to deal with it.

Thinking of dropping my ph down below 7 and do a bunch of brushing with the plastic brush for a few days. Aggressive brushing with a ss brush gets most off, but not sure what's worse for the plaster. I think it's a 6-half dozen sort of thing.

 

[JamesW]

Sand can adhere to plaster under scaling conditions.

However, quartz sand won't dissolve in acid.

Try some acid on typical sand around the pool area to see if it dissolves.

Just maintain ph at 7.2 and brush as much as possible.

 

[shoot-straight]

I diluted some acid maybe 20-30 to 1. I put in some of the granules. They started bubbling.

 

[JamesW]

It's calcium carbonate. Hopefully, it will come off without damaging the plaster.