Water balance after closing a plaster pool?

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S

SlowRocker

0
Mar 14, 2015
95
Parker, CO
Evening folks,

Just wondering if anyone checks their water balance after closing. I've been playing around with PoolMath and it seems that as the temps get lower the water drifts towards the iffy zone for plaster pools.

Current readings:
FC – 7
CC – 0
pH – 7.6
TA – 80
CH – 350
CYA – 60
Salt – 3040
No Borates

I entered these numbers and lowered the water temp to 32 and the CSI was -0.63. Does water chemistry not count when the pool is closed?

Just wondering.
 
Great question.

I do know the pH tends to drop a bit in my pool over the winter, though I don't worry about CSI so much since our pool is vinyl lined.
 
Saturn94 said:
Great question.

I do know the pH tends to drop a bit in my pool over the winter, though I don't worry about CSI so much since our pool is vinyl lined.
Click to expand...

Thanks Saturn94. Wondering if you use borates? If you do doesn't that stabilize your pH?

So, I input a lower pH, 7.4, and the CSI is now -0.82. This doesn't look good. I guess an additional question would be what damage would be done to the plaster if left this way over the winter months?
 
Yes, I do use borates. During the summer pH stays rock solid at 7.5. But for some reason after being closed all winter pH usually tests about 7.2 at spring opening.
 
Saturn94 said:
Yes, I do use borates. During the summer pH stays rock solid at 7.5. But for some reason after being closed all winter pH usually tests about 7.2 at spring opening.
Click to expand...

Thanks again Saturn. More to consider.

- - - Updated - - -

MarianParoo said:
Calling Chem Geek! I am curious about this!
Click to expand...

That would be most helpful. Thanks Marian! (why am I imagining a Bat-Chem-Geek-Signal :D)
 
Normally, when the water temperature drops, the pH rises and that compensates for the CSI to keep it fairly stable. Of course, other things can happen to move the pH, but the temperature effect would have the pH rise when the temperature drops and then the pH would drop again when the temperature rose back up.

With the water being so cold you don't need to worry as much about the CSI for plaster since any negative effects would be very slow (within reason -- the pH shouldn't drop very much even if it did for some reason).
 
Vinyl pools react differently from plaster and cement based pools. You may find that the pH rises slowly over time in plaster pools.

I suggest that you check the pH once a month to make sure it doesn't go higher than 8.0. If the pH goes over 8.2, then scaling is possible.
 
chem geek said:
Normally, when the water temperature drops, the pH rises and that compensates for the CSI to keep it fairly stable. Of course, other things can happen to move the pH, but the temperature effect would have the pH rise when the temperature drops and then the pH would drop again when the temperature rose back up.

With the water being so cold you don't need to worry as much about the CSI for plaster since any negative effects would be very slow (within reason -- the pH shouldn't drop very much even if it did for some reason).
Click to expand...

Thanks for the reply Chem Geek. Makes me feel better. I guess I got a little carried away with PoolMath, but with a major investment in our backyard, I'd rather err on the safe side.
 

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onBalance said:
Vinyl pools react differently from plaster and cement based pools. You may find that the pH rises slowly over time in plaster pools.

I suggest that you check the pH once a month to make sure it doesn't go higher than 8.0. If the pH goes over 8.2, then scaling is possible.
Click to expand...

Thanks onBalance. Appreciate the input. The pH goes from about 7.5 to 7.8 every 3 days. I add about a 1/3 of a jug of acid, and the cycle starts again in a few days. So, I guess we should be ok, but I will take your advice and check every so often.

BTW, thank you for the post on bi-carb startup. I convinced our builder to use that when we started to fill. Although, he wouldn't bite on the entire process (fearing warranty issues) we did follow about 80% of your suggestions.
 
Once the water temperature lowers to very cold temperatures and/or a pool cover is placed over the pool, then the pH rise will slow down a lot and won't need testing and adjusting as often as it does now.
So just to be clear, my first response was based on closing the pool and very cold or freezing water temperatures.
 
onBalance said:
Once the water temperature lowers to very cold temperatures and/or a pool cover is placed over the pool, then the pH rise will slow down a lot and won't need testing and adjusting as often as it does now.
So just to be clear, my first response was based on closing the pool and very cold or freezing water temperatures.
Click to expand...

Our cover is a mesh cover not a solid. Will that matter? Temps are already dropping the 40's overnight, so the water temp should be pretty low once we close. We're having one more hurrah this weekend, running the heater, and I'll turn off the heater to the pool for the season.
 
A mesh cover will allow the water to lose carbon dioxide, which means that the pH will rise faster than if the cover was solid vinyl.
Therefore, you may want to test the pH more frequently than I suggested earlier. Perhaps once a week during winter time.
 
onBalance said:
A mesh cover will allow the water to lose carbon dioxide, which means that the pH will rise faster than if the cover was solid vinyl.
Therefore, you may want to test the pH more frequently than I suggested earlier. Perhaps once a week during winter time.
Click to expand...

At the risk of stating the obvious, the mesh cover (which I also have), since allowing water to pass through it, will have an impact on water chemistry. With my newly replastered pool last winter, I had to adjust the pH probably 7-8 times and would have continued but of course at some point the water froze. Strangely, my pH has continued to go up over the past few months, and this really should no longer be attributable to the plaster. So I'll probably wind up doing the same this winter. My goal is always to keep the SI as close to zero as possible. Being on the alkaline side is safer than being negative. You can always take it off (scale) but you can't put it back on (etching).
 
three4rd said:
At the risk of stating the obvious, the mesh cover (which I also have), since allowing water to pass through it, will have an impact on water chemistry. With my newly replastered pool last winter, I had to adjust the pH probably 7-8 times and would have continued but of course at some point the water froze. Strangely, my pH has continued to go up over the past few months, and this really should no longer be attributable to the plaster. So I'll probably wind up doing the same this winter. My goal is always to keep the SI as close to zero as possible. Being on the alkaline side is safer than being negative. You can always take it off (scale) but you can't put it back on (etching).
Click to expand...

Thanks three4rd. Your post now makes me think about the portion of water that's not frozen. Wouldn't the pH continue to rise under the frozen portion? According to the post by onBalance and Chem Geek it could continue to rise albeit slowly.

Ever try to break through the ice to add acid? :)
 
The pH won't rise from outgassing under the ice since no significant amount of gas should be able to escape. The pH rise could still occur from plaster or other sources, but at such cold temperatures that should be fairly slow. It's a moot point since there's not much one can do about it. So long as it doesn't rise so much as to induce calcium carbonate scaling or metal staining, it doesn't matter.
 
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