Does adding Salt increase the PH?

[shcuck]

So I just added salt to my pool yesterday and this morning I noticed that the PH had spiked from 7.2 ish to close to 8.0.

I added 3 cups (24 oz) of Acid to bring it down... But would this have been the result of adding the salt? My PH has remained very stable for the past couple weeks prior to the salt being added.

Thanks

 

[JamesW]

Salt itself does not do anything to raise the pH. However, there will be several things related to adding salt which can raise the pH.

There will be some aeration from adding the salt, which will cause the pH to rise. Since the plaster is still new, the pH will rise due to the calcium hydroxide being released. When adding the salt, it is common to brush well to get the salt to dissolve. Brushing new plaster will release more calcium hydroxide. Salt coming into contact with the plaster can cause more calcium hydroxide and calcium carbonate to be released.

Have you been brushing regularly?

What are all of your readings including water temperature?

 

[shcuck]

Thanks for the info.

Yes for the first 4 weeks I was brushing twice daily. Now I am only doing it once per day.

Before I added the salt my readings were the following:

FC=3.5
CC=0
TC=3.5
PH=7.2
TA=60
CH=430
CYA=50
Water Temp today is 70F
Thoughts?

 

[chem geek]

What brand of salt did you use? It's possible that it wasn't as pure as it should be and had some base in it.

 

[shcuck]

Brand is AquaSalt...

 

[chem geek]

Well, AquaSalt claims to be >99% pure and if done by evaporation of salt water, it's unlikely to have basic chemicals (i.e. sodium hydroxide) in it. It's more likely the side effects that James mentioned. At any rate, pH is easily adjusted.

 

[shcuck]

Thanks guys, Yeah, the MA I put in this morning should help bring it back down. I was just curious on the effects of adding the salt.

 

[JamesW]

Before adding the salt, the water was already aggressive to the new plaster (-0.49). The addition of salt made it even more aggressive (-0.69). The more aggressive the water is, the more calcium hydroxide and calcium carbonate will be dissolved out of the plaster.

My preference is to keep the balance only slightly negative (-0.1 to -0.3) to prevent scaling. This will greatly reduce the pH and calcium rise due to the new plaster. However, you need to be careful not allow the balance to get too high or you could get scale.

You can use the pool calculator for determining where your balance is.

Based on your current numbers, I would leave the pH at 7.7. If you're planning to heat the pool soon, then I would set the pH at 7.6.

 

[shcuck]

So looks like my PH is back down to normal at 7.5... Now I just need to monitor it and make sure it does not continue to spike.

Thanks again guys