CSI Help

[kraftchick]

Paying more attention to CSI now after Jandy JXI heater installed, and per heater installer recommendation to balance the water consistently. So, up to this point all has been good and I have track CSI turned on in Pool Math app. Temperature of pool dropped quite a bit the last week and half or so, down to 50 this morning. Ran a full set of numbers today and have noticed the CSI creeping out of range. Can you anyone suggest based on the number below, what I might should adjust first to bring water back to a more balance state?

FC 2
CC 0
pH 7.5
TA 60
CH 225
CYA 30
Temp 50F
CSI -0.67

I don't know exact salt ppm number, but this is a new pool this year, fresh fill and I was right at 3500ppm when we first setup the water. SWCG has not been alerting low salt, so I know it's not had enough backwash, etc. to lower it below SWCG's happy level, but surely it's below 3500 after a season of backwashing

 

[Texas Splash]

Keep in mind that CSI is a tool used primarily to manage water for plaster pool products to prevent erosion or scale. That said, if a CSI drops extremely low, it means something is influencing it like a low pH, CH, or water temp. So overall CSI doesn't really apply to your pool (vinyl). For the heater specifically, some manufactures might state a minimum CH level, but it's generally a low pH you should be concerned about. A low pH is the most damaging to your heater core/element. Your pH right now is fine. As the water gets cold, your pH should rise a bit. If the pH stays in the 7.5 - 8.0 range you are in good shape. But if you find the pH begins to fall below 7.4, you can increase the TA a bit (try 80 - 90) and that should help the pH rise if needed.

 

[kraftchick]

Keep in mind that CSI is a tool used primarily to manage water for plaster pool products to prevent erosion or scale. That said, if a CSI drops extremely low, it means something is influencing it like a low pH, CH, or water temp. So overall CSI doesn't really apply to your pool (vinyl). For the heater specifically, some manufactures might state a minimum CH level, but it's generally a low pH you should be concerned about. A low pH is the most damaging to your heater core/element. Your pH right now is fine. As the water gets cold, your pH should rise a bit. If the pH stays in the 7.5 - 8.0 range you are in good shape. But if you find the pH begins to fall below 7.4, you can increase the TA a bit (try 80 - 90) and that should help the pH rise if needed.

Thanks Texas......yes, the heater core/element is the primary focus of my concern and reason I am following CSI (was recommended to use Orenda app and balance to LSI numbers), but most folks here stated they follow CSI, so I will to. Originally (and most of this season) I had a CH of 25 (I never added anything to the water to increase it after filling).....until we decided to install a heater the beginning in September. Even though we're a vinyl pool, recommendation to get water more balanced, was to bring up the CH.....so I brought it to 300 mid Sep, beginning of Oct. it was 250, and as you can see in the numbers I did today, 225.

Couple things I've observed over the last 1 1/2-2 months....CSI is falling.....in all my numbers, CH, pH and temp are all what's been falling. Also, I turned off the SWCG as with lower sun, and far less use, FC had climbed to 12. I've learned that SWCG can drive pH up, so I'm thinking that SWCG being off for several days now is playing a part in the pH going from 7.9 to 7.5, and that's driving the CSI number down and out of range. Playing around with the numbers in the Pool Math, it looks like the pH changes have a pretty significant impact on CSI number...small increases in pH, say 7.5 to 7.7 raises CSI back into range. That seems to fall right in line with what you are saying. So rather than rush out and replace the dropped CH, etc.....maybe watch pH and increase it as needed?

 

[JamesW]

I would allow the pH to rise to about 7.8.

In my opinion, a high CSI causing scale in the heat exchanger is more of a risk than a low CSI causing any type of problem.

The temperature in the heat exchanger gets to between 120 and 135 degrees Fahrenheit.

I would balance the CSI to 0.0 at 128 degrees.

 

[JamesW]

CSI is specific to calcite (calcium carbonate).

It has nothing to do with copper solubility.

Copper is lost to oxidation, low pH and mechanical erosion.

One theory is that a thin layer of calcium carbonate scale can help insulate the copper from chemical attack from low pH or oxidation, but that is virtually impossible to do without triggering a scale buildup due to the thin layer acting as a base or seed for further accumulation of calcium carbonate scale.

 

[kraftchick]

Apologies, I shoulda have mentioned that the heater isn't running (done for the season) and there's no bypass, so that water is constantly passing through the heat exchanger......which is why I mentioned the current 50F water temp

 

[JamesW]

The heater uses a thermal regulator, which prevents water from exiting the heat exchanger until it gets to 120 degrees.

There are a few tiny holes that allow some water to bypass the heat exchanger, but the flow is only a trickle.

I would not be concerned about the calcium or the CSI.

I would keep the pH at about 7.8.