Don't Want a Repeat Scenario Next Spring

[GDK]

So in April 2021 we had our 26 year old pool re-plastered after a make over the previous Fall (View Picts Here). Several weeks after filling, I converted to Salt and the only issue I had was a constant fight a rising pH. Other than that, everything was fine that summer with the pool. I closed in mid-October, using a solid safety cover, and had these test results:

FC - 7.0 pH - 8 TA - 70 CH - 400

So this spring, I opened in late March only to discover that I had calcium nodules on the walls and floor, and in a couple places on the walls there were solid streaks of the white material. My first test readings after opening were:

FC - 0.0
pH - >8.2 (very bright red)
TA - 65
CH - 350

After reading what some others on this forum had done to get rid of them, over the summer I've kept the CSI to around -.4 and scrubbed to get the plaster smooth again. It was a lot of work but it's done. I just do not want to repeat the process again next year.

I will be closing in a few days and would like to know what I can do to not have a repeat situation next spring. I lowered the TA this season and that helped with slowing down the pH rise. Also, I've just pumped about 6 inches of water out of the pool after the IAN NorEaster that dumped lots of rain here in MD. My current test levels are:

FC - 4.0
pH - 7.5
TA - 60
CH - 300
CSI from Pool Math reads -.62
Are these levels acceptable to close?

I was wondering I worked to keep the pH at perhaps 7.5 or so throughout the winter would that help? Every month or so I can pull a sample of water and see what's happening to the pH and then add liquid acid to the deep end if the pH starts to rise again. And oh, a little liquid chlorine if needed.

Any thoughts? TIA,
Gary.

 

[Jimrahbe]

Gary,

Calcium nodules are not really a chemical issue but rather a poor bond between your old plaster and your new plaster.

Thanks,

Jim R.

 

[Newdude]

Have a read.

Calcium Nodules in pools

What are calcium nodules? In swimming pools and spas, they are small mounds, bumps, deposits, or “slag” piles of calcium carbonate which are formed from material that has been released from the plaster. The small calcium nodules are rough to the touch, hard, and generally gritty. Nodules may...

www.troublefreepool.com

 

[JoyfulNoise]

@onBalance might have a few suggestions but I agree that nodules aren’t as much a water chemistry issue and they are an issue with the surface integrity of the plaster.

Also, there would be no harm in adding a startup dose of calcium sequestering agent to the pool before closing. ScaleTec is a very solid product.

 

[GDK]

Thanks for the references.

So does anyone know if the nodule production will ever stop?

 

[Jimrahbe]

So does anyone know if the nodule production will ever stop?

Gary,

It may, but it is just as likely to continue as more weak spots show up.

Thanks,

Jim R.

 

[onBalance]

Are you sure that the problem is calcium nodules and not calcium crystals all over the pool?
Please take a few close-up photos of the nodules and post here.
Let' s make sure before we go any further. Review this post and let us know which problem it is.

Why Are Calcium Crystals Forming in Pools?

In recent years, calcium crystals have been forming during the winter at a higher rate in some newly plastered swimming pools. From the reports we have heard, this problem seems to occur more often in the northeast of the country. Apparently, pool builders, plasterers, and service techs involved...

www.troublefreepool.com

 

[GDK]

After reading the post you listed and the in-bedded link to the Orenda website article, I had what they showed in the photo of the wall and fingers. They call it calcium crystals.

The sides of the pool felt like a very, very course sandpaper. The particles were very small, like less than a millimeter and rough to the touch. I've gotten most of them off and cannot give you a picture of them. Now I scraped them off back in early summer and so far they do not seem to have returned but the water has been warm, of course.
I do have a few of the things as shown in the second photo, in various places on the walls.

Now wrt my water chemistry, would you recommend that I raise the CH level, and if so, to what?

TIA,
Gary

 

[onBalance]

It is possible that you have both problems; calcium crystals and calcium nodules. The second photo appears to be a small nodule. If similar formations elsewhere are present, then those may be calcium nodules.
In any event, you should balance the water according to the CSI (or LSI).
I suggest you contact the contractor and make them aware of this situation. Neither issue is caused by aggressive water.

 

[JoyfulNoise]

I would still suggest adding a high quality scale inhibitor. One thing that scale inhibitors do is interfere with the crystallization growth process of calcium carbonate. The net effect of that is to retard crystal growth and make it harder for them to form. There’s no downside to adding it other than the hit to your wallet. I would at least give that a try.

 

[GDK]

Thanks