Low calcium, CSI ok

[beth83]

New plaster pool build was filled Aug 1. My TA has been high and my builder says my calcium is fine. My numbers using the Taylor 2006 test kit

FC 7.0
CC 0
PH 7.6
TA 120
CH 170
CYA 60
Salt 4000
CSI -0.30

I'm thinking of closing the pool end of Sept/early Oct but I'm worried that the lowish calcium might cause problems over the winter. Also I'm adding 3 cups of muriatic acid every 3-4 days I assume from what I've read that's normal for a SWG pool?

The builder uses test strips and the color does look closer to the 250 mark for CH than 100 but it's so hard to tell. I definitely like the Taylor kit more. But since my CSI is ok does that mean my pool should be fine?

Also they added way to much salt when starting. Will this level cause a problem with my electric heater in the long run?

 

[mas985]

As long as CSI is just slightly negative, I don't think you have anything to worry about.

Also, because you have a new plaster pool, CH will rise in the next few months so I would not do anything right now.

 

[ajw22]

CSI will decrease as water temperature decreases.

You need a higher CH to keep your CSI above -0.6 when water temperature approaches freezing. Otherwise your water can leach calcium out of your plaster over the winter.

I would get your CH to around 300.

 

[mas985]

CSI will decrease as water temperature decreases.

You need a higher CH to keep your CSI above -0.6 when water temperature approaches freezing. Otherwise your water can leach calcium out of your plaster over the winter.

I woudl get your CH to around 300.

The CSI is currently well above -0.6 and since CH will rise in the coming weeks as the plaster cures, I think raising it at this point risks over shooting. I would hold off and monitor CSI over the coming weeks.

Also as OnBalance has shown, leaching of Calcium is a very slow process even at CSI levels as low as -1. Leaching at this point is extremely low risk.

 

[ajw22]

The CSI is currently well above -0.6 and since CH will rise in the coming weeks as the plaster cures, I think raising it at this point risks over shooting.

What values do you consider over shooting?

@beth83 is considering closing in 4 to 6 weeks. What CH range should she have at closing?

 

[mas985]

It is far easier to add CH than it is to remove it so I am always a little cautious about adding CH when it isn't absolutely necessary. Especially for a curing plaster pool.

As the temperature drops, CSI will also drop, this is true. However, the OP is currently adding MA to keep PH down and as
the water temps drop, they can instead just not add as much MA to the water and let PH rise to keep CSI in range. After closing, it is my belief is that PH and CH will only increase because of the curing plaster.

For example, if PH is allowed to go up to 8.0 and the water temperature is close to freezing, CSI is still above -0.4 but that is assuming CH does not change which I believe it will. It will only need to increase to 200 ppm to have a CSI of -0.3.

I would monitor the CSI until closing at which time, the OP can decide if they need to add CH or not. If CH remains stable during this time and PH does not rise, then CH probably should be added. However, if PH rises to a higher range and CH also increases, then maybe it is not needed.

 

[beth83]

Thank you both for the advice. I'll continue to monitor the CSI and CH as I get closer to pool closing time. I'm still getting used to all this with being a new pool owner.

 

[beth83]

I have another CSI question. All of my numbers are within the recommended ranges (minus salt) but my CSI is still a bit low. I'm probably overthinking this but I'm new to maintaining my new pool and want it to stay nice (and I like numbers). It was filled on Aug 1 so plaster is still curing. My numbers...

FC 6
CC 0
PH 7.6
TA 80
CH 250
CYA 60
Salt 3700
Temp 76
CSI -0.38

I've been adding MA about every 4 days when it gets to 8. Also do people adjust their pool chemicals when it starts getting colder? I noticed when playing around with the numbers CSI changes quite a bit with the temperature. Our heater is back on for a few warm days here coming up in MD but will turn off heater after that again. What is the easiest/best way to keep the pool balanced (add calcium?, raise Alk?) as I'm getting close to closing for winter.

 

[PoolGate]

There is nothing wrong with your CSI.

 

[mas985]

You really don't need to worry too much unless CSI gets well below -0.6 but even then, a short period of time is not an issue. Also, even if your water temperature goes to 32F, CSI is around -0.8 and I don't see that as a huge problem as I have been there on my own pool on several occasions without consequences.

I noticed that CH has climbed from 170 ppm to 250 ppm. Have you added any CH or is that all from the plaster/fill water?

Are you still adding acid? If so, I would stop and see where everything levels out. CH may still rise due to plaster curing and PH will likely rise as well over time. So by the time you close the pool, everything should be good to go.

 

[beth83]

I added CH because it had been at 170 for weeks and was worried about it being so low. I'm not planning on adding anymore.

My pH test tops out at 8 so I was worried about it going above 8 without me being able to tell.

 

[ajw22]

My pH test tops out at 8 so I was worried about it going above 8 without me being able to tell.

The test tells you your pH is above 8 which is all you need to know.

When your pH is above 8 lower it into the 7s.

 

[mas985]

I added CH because it had been at 170 for weeks and was worried about it being so low. I'm not planning on adding anymore.

My pH test tops out at 8 so I was worried about it going above 8 without me being able to tell.

I think you are fighting yourself. You are concerned about CSI but you keep adding MA which keeps CSI very low. Don't forget that TA also drops when adding MA making CSI even lower. Plus, PH does not rise that quickly after adding MA unless you have a lot of aeration so you have plenty of time to make adjustments.

I don't think you have too much worry about PH getting too high. PH would have to climb to 8.4 before CSI becomes 0 (@32F) and I don't think PH will get that high due to the current TA level.

Lastly, some PH test kits come with acid demand reagent that allows you to determine PH levels above 8.0.