Pool Opening: How to Remove Calcium Scale?

[njbobcat23]

Hello, all.

I removed my pool cover this afternoon to discover decently clear water in my pool, but a fuzzy coating of crystaline calcium scale along the walls and floor. What I could reach comes off pretty easily with my hand, so it isn't "baked on". What should I do to the water to get the calcium to redissolve? Can I add acid and lower the pH sufficiently enough to get the calcium scale to redissove? Or is there another way to remove it?

Following is a bit of background information.

21000 gallon pool built in 2007 in central NJ with Hydrazzo finish, DE filter, chlorinated with the Liquidator. I switched to the BBB method of pool maintenance at the start of the 2008 season, so I'm still fairly new to the process.

Current test results:

FC/CC/TC: 0/0/0
ph: > 8.0 (off scale, very bright red)
TA: 50
CYA: 0
CH: 120

Also, when the pool was closed at the end of last September, these were the test results:

FC/CC/TC: 0.4/0/0.4
pH: 7.6
TA: 120
CYA: 35
CH: 260

From what I've seen here and elsewhere, the scaling is likely a result of the pH creeping up over 8.0. How can I prevent that from happening over the winter months? Should I close the pool with a lower pH? I use a mesh safety cover, so rain and snow melt does get into the pool when it is closed. Does rain water cause the pH to creep up or is something else driving it? Is it typical to have to monitor the pool over the winter months and amend the water for a completely closed pool? I don't know anybody around my parts doing that.

Thanks for any insight,
Bob M.

 

[Guest]

I would lower the TA when you close. If you notice you lost both CH and TA while the pool was closed. The two combined to form your scale that you now see.
Keeping the pH low for a week or three might help dissolve it (and cause your CH reading to rise also)
When you get around to adjusting the water don't bring the TA up any higher than about 70 ppm for right now.
I understand exactly why this happened but the explanation is technical. Suffice to say it was a combination of mesh cover, high TA and normal calcium that caused it. If you had a solid cover it possibly would not have happened.

BTW, the fact that your CYA disappeared indicates that you might have a large chlorine demand at first. If so, just keep shocking until the FC holds. It might take a while and a lot of bleach but it will eventually hold.

 

[njbobcat23]

Waterbear,

Thanks for the reply. A few follow-up questions:

How low should I take the pH to facilitate the calcium absorption? Am I better off holding off on the brushing and breaking loose the crystals for a bit? I'm thinking that the loose crystals will quickly clog up my filter once I start the pump.

Should I raise CYA before or after the initial shock? Or simultaneously?

At what level should I target TA, pH, and CH when I close the pool next fall?

Bob

 

[ssummer]

njbobcat23: I'm having this exact issue with my pool in South NJ that I just opened up two days ago. Being as you went through this a few years ago, do you have any advice or input as to what worked/didn't work to fix this?

Thanks!

 

[njbobcat23]

ssummer,

I decided not to attempt to fix the problem chemically, mainly because there was no guarantee it would work and it might take awhile if it did. I also discovered I could not brush the scale off the the pool walls and floor after I got about 18 inches deep and even if I could, I didn't want all that scale in the filter. In the end, I wound up dumping the pool. Luckily I have a good place to direct that much water that doesn't turn the yard into a soggy mess. Once the scale was exposed to the air and sun, it dried quickly and flaked off very easily with a broom or a drywall taping knife. I swept the entire pool into the deep end and collected about 30 pounds of the scale residue. It took 3 days to refill the pool with a hose. Aside from the aggravation and the time, it only cost me about $125 for the water and a bag of calcium chloride to bring up the CH in the new water. An added benefit was that I started the year with a perfectly clean pool and water that was easy to get balanced right out of the gate.

Unfortunately, I went through this routine a couple more times in 2009 and 2010, but each time the amount of scale was less than the year before. The last two seasons, I had no scale. I have altered the pool chemistry I keep over the summer and at close-up time. I keep the TA below 90 and the CH around 220. I do fight with PH creep and end up using about a quart of muriatic acid every 2-3 weeks to keep it at 7.6. I did think about getting a solid cover as it was suggested that the mesh cover might have been contributing to it, but did not mainly because I could still (barely) handle the mesh cover by myself but knew that I would have to get some helpers (or hire somebody) to take off and put on the solid cover each year.

I hope this helps. Good luck with the new pool...

Bob

 

[ssummer]

Thanks for the help Bob...it's good to hear that the solution wasn't too bad, although it does still seem like a big pain. I talked to my pool builder yesterday, and he said that it is very common for new concrete pools in our area, especially with the swg and seemed to think that once I got my chemicals in order it, it would loosen the material up and brush off after a week or two. He also suggested a product called ScaleTec...I think I might give it a try after reading some of the reviews.

Thanks again for all the help...good luck to you...