Rising CH in New Pool

[Miniguy77]

That's right.

The new plaster will keep the pH on the rise.

So after all this discussion I’m still at a loss to explain the relatively rapid rise in CH. Can this occur with new plaster, which BTW contains quartz. It is an NPT Pool product called Quartzscapes.
I ordered a Speedstir today from the TFT website.

 

[mknauss]

Some of the rise could be due to the initial burst of calcium released after the plaster. Though it seems your testing did not show that.

You said you raised your CH. I assume by using calcium chloride. Did you test the CH after adding that to confirm the rise you expected?

 

[mknauss]

I know you say you do not have any evaporation - but - if your pool water is 80F and your outside air is below that, you are getting significant evaporation. The question is what is replacing that.

 

[IceShadow]

Calcium doesn’t leave your pool when water evaporates. It evaporates, you add water - this water has more calcium. Repeat often and CH will go up.

 

[Miniguy77]

Some of the rise could be due to the initial burst of calcium released after the plaster. Though it seems your testing did not show that.

You said you raised your CH. I assume by using calcium chloride. Did you test the CH after adding that to confirm the rise you expected?

The calcium chloride was added by the contractor who said he brought it up to 240. When I tested it last month it was about 275.

 

[Miniguy77]

I know you say you do not have any evaporation - but - if your pool water is 80F and your outside air is below that, you are getting significant evaporation. The question is what is replacing that.

That’s the $64 question. I would say over the past month, on average, the pool and air temps have been fairly close, within a few degrees, with the pool maybe just a little higher.

 

[mknauss]

Does your auto fill have a valve to it? Turn it off, see if the water level drops.

 

[Miniguy77]

Does your auto fill have a valve to it? Turn it off, see if the water level drops.

Did it

 

[arvil]

If it rains frequently as here in PA, rain has no CH, it'll drop. Fill water adds some CH depending on location.

 

[arvil]

I lower pH with MA. Over a week or two, pH rises due to carbonates (part of TA) creating carbonic acid to an equilibrium, the carbonic forms CO2 in solution which gases off. pH slowly rises, then I add more MA, TA decreases.

 

[Miniguy77]

Does your auto fill have a valve to it? Turn it off, see if the water level drops.

I put a mark on the tile at the water line. Let’s see what happens after a day or two.

 

[Miniguy77]

The calcium chloride was added by the contractor who said he brought it up to 240. When I tested it last month it was about 275.

Just thought of something else. Over the July 4 weekend, I heated up the spa for the grandkids a few different times. It was the first heating on the new plaster since pool was filled 2 months prior. The spa water eventually dumped into the pool. Is it possible that could have caused CH to increase?

 

[mknauss]

Just thought of something else. Over the July 4 weekend, I heated up the spa for the grandkids a few different times. It was the first heating on the new plaster since pool was filled 2 months prior. The spa water eventually dumped into the pool. Is it possible that could have caused CH to increase?

Should not have.

 

[mknauss]

Use Effects of Adding Chemicals to see how many pounds of calcium chloride you would have had to add to raise your CH as much as it has. You will be surprised how much it is.

 

[Miniguy77]

Use Effects of Adding Chemicals to see how many pounds of calcium chloride you would have had to add to raise your CH as much as it has. You will be surprised how much it is.

Yeah, upwards of 20 pounds. It was a long shot question. Only reason I asked is that the pool contractor warned me at the outset no spa heat for 30 days.

 

[mknauss]

That is because of plaster dust in the water coating on the heat exchanger tubes.

 

[Miniguy77]

Does your auto fill have a valve to it? Turn it off, see if the water level drops.

Did it

So 24 hours now after shutting the valve to the auto fill and marking the tile at the water line, the level has gone down about 1/4”. So, regardless of what I said yesterday, the auto fill is working to replace water lost from evaporation. But that doesn’t solve the mystery of why the CH has increased 100 ppm over the last 30 days or so. This morning I got 375. According to pool math, 40% of the pool, or 9600 gallons, would have had to evaporate to raise CH by 100 ppm (check me on this). If I take the 1/4” daily loss over the past 30 days or so, that’s a total loss of 8”, which translates to about 2,000 gallons for my approximate 400 sq ft of pool surface - that’s only about a fifth of the pool math calculation. And that’s not even accounting for the month of June with a high percentage of cloudy days with humidity 70-80%. We only started getting sunny days a week ago.
So I can only guess that maybe it still has something to do with the new plaster. And, more importantly, is this a trend that will continue for some time, to the extent of my having to replace a fair amount of pool water?

 

[mknauss]

The new plaster should not raise your CH after the initial burst. Still odd to get that much rise in that short of a time. Your evaporation is less than I suspected. I would say monitor the CH with weekly readings and see what it says.

 

[Miniguy77]

The new plaster should not raise your CH after the initial burst. Still odd to get that much rise in that short of a time. Your evaporation is less than I suspected. I would say monitor the CH with weekly readings and see what it says.

So I took a reading with my new Speedstir. Using the 10ml sample, it turned light blue after 14 drops (350 ppm) but I was able to push it to a medium blue with the Speedstir at that point. Adding the 15th drop turned it a darker blue. So does that mean it’s really 375 ppm?

 

[mknauss]

That would be 375ppm.