CH Drop

[Shock11]

I measured today and my calcium hardness was 250. I measured twice just to make sure. It had been around 350. What would cause such a drop? Poolmath says I need to add about 25lbs to get it back into range.


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[bdavis466]

Rain or a leak. Really the only two ways the CH could have lowered on its own.

Have you had either?

 

[Casey]

Yes, adding water is about the only way it could lower.

 

[Shock11]

Yea forgot about that. We did have a heavy rain Saturday night.


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[tim5055]

A heavy rain wouldn't do it. You would have to replace almost 1/3 of the water in the pool to have that kind of drop.

 

[MarianParoo]

You have a new pool with significant potential issues from the "cloud" the PB created. I think the CH issue may be related. Would you please post this same question on one of your more active previous threads? This thread may be your best option due to the quality of the followers:
Mottling

It is important for us to know your history as you are in the process of dealing with major! issues.

 

[Shock11]

The CH has been normal since the beginning. We had a heavy rain since my last normal test. The chemicals have been testing normal. I'm not sure why my post about the original start up is referenced or would have bearing to CH drop after a significant rainfall.


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[tim5055]

CH drop after a significant rainfall

could the rainfall have displaced over 6,000 gallons of water? It would have had to have spilled over the coping or was pumped out. Did either of those occur?

 

[MarianParoo]

...I'm not sure why my post about the original start up is referenced...

I have just been concerned about your start-up ever since the cloud appeared upon filling. I felt that your history might be important. Good luck with everything!

 

[duraleigh]

I measured today and my calcium hardness was 250. I measured twice just to make sure. It had been around 350. What would cause such a drop? Poolmath says I need to add about 25lbs to get it back into range.

To get back into what range? What does Pool School say about acceptable range for CH.

CH does not drop on it's own. Rainfall won't change it that much. What's left? Testing error is the only thing I can conceive.

 

[Shock11]

could the rainfall have displaced over 6,000 gallons of water? It would have had to have spilled over the coping or was pumped out. Did either of those occur?

It did get drained out through the overflow and into the yard. I seriously doubt I lost 6000 gallons.


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- - - Updated - - -

To get back into what range? What does Pool School say about acceptable range for CH.

CH does not drop on it's own. Rainfall won't change it that much. What's left? Testing error is the only thing I can conceive.

Well I test anything that is not in normal range twice to make sure that it is tested correctly. The only difference is that I used the speed stir. So the only error would be that the speed stir causes a difference in reading due to the amount the solution is mixed.

 

[tim5055]

The only difference is that I used the speed stir. So the only error would be that the speed stir causes a difference in reading due to the amount the solution is mixed.

If you are saying you hand stirred for the 350 result and the speedstir for the 250 result then you have your answer. It is very common for this to drop when changing from hand stirring to usin a speedstir.

 

[WASP]

Test results will be more accurate, consistent or repeatable using the speedstir.

 

[Shock11]

I'm going to pick up some calcium chloride. Being that the pool has been filled for a month, should I raise to 350 or just raise slightly since it's currently 250? They haven't put the salt in yet so I'm still treating it as a bleach pool. Being that the water is 52 degrees, should I dilute in a bucket first or broadcast?

 

[bdavis466]

You need to post a full set of numbers. There are a lot of other factors that come into play and have a direct effect based on the CH level.

 

[Shock11]

PH: 7.8
FC: 3
TA: 60
CC: .5
CH: 250
CYA: not measured


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[bdavis466]

Your numbers are fine where they are now since they yield a CSI of -0.26.

The decision to add calcium is going to based on the CH of your fill water, the rate of evaporation you expect to experience, and the average annual rainfall. I my area, with so little rain, we constantly fight rising calcium levels so adding calcium would only make the problem worse and require a water replacement sooner than if no calcium was added.

Once you add salt to the pool, your CSI will drop further to -0.49 (assuming 3200 ppm and your current numbers). It would be best for you to target a pH of 7.6-7.8 and maintain the TA around 60-70.

Use Pool Math to calculate The CSI for you. Shoot for +0.1 to -0.2

 

[Patrick_B]

You do not need to add Calcium to your pool. Be grateful it is where it is. It will come up in time on its own.

 

[Shock11]

You do not need to add Calcium to your pool. Be grateful it is where it is. It will come up in time on its own.

I thought it was the opposite. I thought that you would not want your CH to be low and pull calcium from the new plaster.

 

[bdavis466]

Other factors play into the aggressiveness of the water, thats what the CSI is for. The actual calcium content in the water has surprisingly little to do with it.

PH has the biggest effect, so keeping the pH on the higher side of things will help (in addition to requiring less acid to maintain), TA has the next biggest impact. Play with some numbers in pool math and see how the CSI changes.

Plaster degradation occurs around -0.7 (which you are well above), and even then, its a slow process.

Your calcium level is fine where it is now. The recommended levels are nothing more than a guideline to simplify things for those that don't use the CSI.