Strategy to Prevent Over-the-Winter Scaling

[njbobcat23]

Hello, all.

I've opened my pool each of the last two springs ('08 and '09) to a fairly severe case of calcium scale. In each case, my recourse was to dump the pool, let the finished surfaces air dry, remove the scale with a stiff broom, sweep it up, and refill. There was less this year than in 2008, but still a significant amount. I want very much to avoid doing that again in the spring of 2010.

First, here is some background on my pool:

20500 gallons, built in 2007 in central NJ with Hydrazzo finish, DE filter, chlorinated with the Liquidator. I use a mesh safety cover over the winter, so rain and snow melt do get into the pool.

When the pool was closed at the end of September 2008, these were the test results:

FC/CC/TC: 0.4/0/0.4
pH: 7.6
TA: 120
CYA: 35
CH: 260
Temp: 72

These were the test results when I opened in May 2009:

FC/CC/TC: 0/0/0
ph: > 8.0 (off scale, very bright red)
TA: 50
CYA: 0
CH: 120
Temp: 58

And these are my current numbers:

FC/CC/TC: 1.6/0/1.6
pH: 7.6
TA: 90
CYA: 30
CH: 210
Temp: 88

I've generally figured out that the reason the scaling is happening is that the pH drifts upward over 8.0 over the winter and that combined with cold water and moderate levels of TA and CH create the scale deposits.

So, here are my questions:

What is driving the pH up?

Should I close the pool with a lower pH, TA, and/or CH? If so, what levels?

Does rain water cause the pH to creep up?

Is it typical to have to monitor the pool over the winter months and amend the water for a closed pool? I don't know anybody around my parts doing that.

Thanks for any insight.

Bob

 

[frustratedpoolmom]

I would lower the PH down to 7.2 before you close. You don't want to go lower on your CH.

Yes, rain drops can cause aeration and slight ph rise. What's odd is your TA and CH levels were affected. How are you testing?

Some people do put in a small submersible pump to circulate the water from time to time if adding chems mid season (areas where it doesn't freeze).

Is there a particular reason your chlorine is so low?

 

[Butch]

Great question, as I too am wondering the same thing.
I had scaling issues this spring and I am suspecting due to the PH being crazy high.
I have been fighting PH drift all season even with a TA of 60.
I am able to keep everything else stable but PH I cannot get a handle on.
Suggestions?

 

[frustratedpoolmom]

Great question, as I too am wondering the same thing.
I had scaling issues this spring and I am suspecting due to the PH being crazy high.
I have been fighting PH drift all season even with a TA of 60.
I am able to keep everything else stable but PH I cannot get a handle on.
Suggestions?

Please start your own thread, and when you do, post a full set of test results.

 

[dmanb2b]

NJ...you can lowere your PH to 7.2 as FPM suggested before closing and you may also want to lower your TA to 70 as well...this may help the PH rise over the winter.

 

[njbobcat23]

FPM and DMAN,

Thanks for the suggestions. I should also note that I fight an upward pH drift during the summer months, too. Enough to use a quart of acid every other week or so. My TA has fluctuated around 100 all summer. After I filled the pool in May, I added calcium chloride to raise the CH to about 220. We've had a lot of rain lately so that is probably why it has come down some.

Regarding testing, I use one of the Taylor test kits so I think I'm doing a consistent and accurate job of testing the water. My assumption about the lowered CH in the spring is that the calcium in the water scaled out, and dropped the CH accordingly. Is that a good assumption?

And, yes, my FC is a bit low. I typically keep it in the 3.0 range...

Regards,
Bob

 

[frustratedpoolmom]

Yes it's a good assumption. I agree, keeping the TA on the lower end may help your PH stabilize during the summer.