Salt for SWG versus Calcium Chloride

[jesse-99]

Just double checking... I ordered some Snow Joe Calcium Chloride to bring up my CH a little bit (it was at 250). That kind of salt is different than the salt added by my pool equipment guy for SWGs, correct? My salinity won't go up because I added a bit of Calcium Chloride?

 

[JamesW]

The salinity will go up by almost as much as adding sodium chloride.

 

[mgtfp]

But since you usually don't add CaCl₂ in 20-25kg bags as you would with NaCl, you shouldn't mess up your salt level too much.

 

[jesse-99]

I added about 10 pounds today. Pool Math wanted me to add around 22 pounds but, I did less than half of that to see what it does and recheck...

 

[JamesW]

 

[jesse-99]

I added 10 pounds of Calcium Chloride. So I'd expect CH to go up by 34. (according to Pool math)

 

[mgtfp]

The PPM change of your salt by adding Calcium Chloride is of the same order (not exactly the same number, but similar) of the PPM change of the CH-level. So, unless you want to change your CH level by hundreds of PPMs (which I hope is not what you are intending), you will probably hardly see a relevant change in the salt level.

And before trying to chase the "perfect" CH, consider how your CH changes over the course of the year due to topping up with potentially high-CH fill water. It is a one-way road - easy to increase CH, but not easy to get it down. As long as the CSI is acceptable , there is not really a need to mess with it.

And make sure to have a reliable CH-reading before adding more Calcium Chloride. I would not recommend to add any Calcium Chloride based on test strip or pool shop testing.

 

[JamesW]

I added 10 pounds of Calcium Chloride. So I'd expect CH to go up by 34. (according to Pool math)

That's correct.

The salt will go up by about the same amount as the calcium hardness.

If your CH goes up by 34, the salt will go up by 34.

 

[jesse-99]

My auto-fill tests out at 150 for CH... so more auto-filling shouldn't cause my CH to shoot up. I'm targeting around 300 for CH (was 250 before the addition of the Calcium Chloride today) .. using a TF-PRO.

 

[mgtfp]

.. using a TF-PRO.

Cool, all good then.

auto-fill tests out at 150 for CH... so more auto-filling shouldn't cause my CH to shoot up

It really depends on how much evaporated water you are topping up with fill water vs. rain water.

You add fill water with calcium. When water evaporates, it leaves this calcium back in the water. Topping up with more fill water will add more calcium. With more and more of these cycles, CH will increase, even though your fill water's CH is lower than the pool's CH.

It's good to understand how your pool behaves (depending on evaporation water loss, fill water CH and amount of rain water).

In my case for example, I have soft fill water (CH around 20-40ppm), and I usually get a lot of rain over winter, so I have learned that over time my CH trends downwards, and I have to add some Calcium Chloride from time to time. But with harder water, higher temperatures and less rain, that trend can be in the other direction.

 

[jesse-99]

Great info, thanks!.

 

[jesse-99]

You add fill water with calcium. When water evaporates, it leaves this calcium back in the water. Topping up with more fill water will add more calcium. With more and more of these cycles, CH will increase, even though your fill water's CH is lower than the pool's CH.

It's good to understand how your pool behaves (depending on evaporation water loss, fill water CH and amount of rain water).

FYI -- this is what is helpful to know. I didn't take that into account. I probably shouldn't have added the 10 pounds of Calcium Chloride today knowing that with evaporation, the calcium stays in the water. Oh well. Lesson learned.

 

[mgtfp]

CH of 300ppm is still on the lower side, you will be fine.

Sorry for not associating your name straight away with our long chat in your other thread regarding testing, got that first mixed up with another thread where test strips were used. Of course you are using the TF kit...

But as mentioned in the other thread, your CSI is OK unless you maintain pH too low. Just watch how your CH develops over time, and you'll work out if you need to increase CH from time time, or whether you'd rather avoid calcium chloride.

 

[mgtfp]

Thanks for your comment in that other thread on your experience with test strips. That was exactly the thread I was referring to in my last post that I got muddled up in my head with your thread.