Last Question for a while--CH at 470. Is this a problem?

[Species 8472]

The rest of my numbers are fine. Should I just live with it until it declines with water spill out?

If so, what are the consequences?

Sorry about the multiple posts....Just modulating everything now that I have my own test kit and had things screwed up by pool store.

 

[bdavis466]

Your CH level is fine and will prove to be a benefit with your SWG. Keep and eye on your pH and how it relates to the CSI. Keep the CSI of you pool slightly negative and that should take care of any potential issues with scaling.

Additional reading HERE.

 

[jblizzle]

I would disagree with Brain a bit here. Having a higher CH does not benefit the SWG ... in fact it raises the likelihood of scaling in the cell if the pH is allowed to get too high.

I do agree you want to keep the CSI slightly negative .... so the pH may need to be a little lower due to the higher CH.

 

[bdavis466]

It is a benefit in regards to the CSI since the recommended levels produce such a low CSI index. With the pH, TA, CYA, Salt, and potentially borates at the suggested levels, the CSI is vey near -0.6. Really the only way to compensate for the low index is to have a higher level of CH.

The post I referenced by Chem Geek covers this in detail

I do agree though that if TA and pH are allowed to get high, having more CH in the pool greatly increases the chances of scale...One just needs to pay attention to the CSI.

 

[jblizzle]

Who said anything about borates?
And with no mention of the TA and pH ... not worth making generalizations like that IMO.

 

[chem geek]

If we had a complete set of test results, we could answer the question more specifically, but if you put your result into PoolMath and get a CSI that is slightly negative (i.e. -0.2 or -0.1) then there's no problem. Even with 0.0 or positive you'll only have some scaling in the salt cell and if you use 50 ppm Borates that is minimized. If you were pushing +0.3 or more, then that might require more cleaning of the salt cell than you'd want and each cleaning reduces the life of the cell somewhat.

 

[Species 8472]

Here are my numbers:

Added 13 boxes of 20 mule borax on Sunday based on a prior pool store reading of 12 ppm. This should put me in the 30 to 40 range

PH: 7.6
FC: 2.0
CC: 0.0
TA: 100
CYA: 60 to 70
CH: 470
Salt: 4200 PPM

I should get my borate test in the next few days, and will adjust accordingly.

- - - Updated - - -

Oh yeah....Pool Temp is 87 degrees. Love that darker plaster and no shade on the pool!

 

[chem geek]

Your CSI at 87ºF is just above zero (+0.05 using my spreadsheet). So you aren't in bad shape so long as our pH doesn't rise too much. You can probably get your TA down as that will help reduce the possibility of pH rising as fast. In fact, with your numbers, if you get your TA to 70 ppm and don't worry if your pH gets to 7.7, then your CSI will be around -0.07 which is fine. If you don't get much scale in your salt cell in this situation, then you'll be in great shape. If you wanted your CSI a touch lower, you could just target the pH down a bit to 7.6. So really you're not in a bad situation at all with the CH where you have it.

 

[Species 8472]

Your CSI at 87ºF is just above zero (+0.05 using my spreadsheet). So you aren't in bad shape so long as our pH doesn't rise too much. You can probably get your TA down as that will help reduce the possibility of pH rising as fast. In fact, with your numbers, if you get your TA to 70 ppm and don't worry if your pH gets to 7.7, then your CSI will be around -0.07 which is fine. If you don't get much scale in your salt cell in this situation, then you'll be in great shape. If you wanted your CSI a touch lower, you could just target the pH down a bit to 7.6. So really you're not in a bad situation at all with the CH where you have it.

Thank you so much for the above information! I now have to take a look at your CSI index and learn aspect of pool maintenance. My pool is now a year old so I suspect there will be even more PH creep. I will throw in a bit more CYA and Muriatic acid tonight as it is supposed to rain in my area tonight and tomorrow.

 

[bdavis466]

Who said anything about borates?

Borates have been recommended many times for SWG pools because of their ability to buffer pH and reduce scale formation in the cell.

And with no mention of the TA and pH

A CH value alone is not enough to determine scale potential. I mentioned pH, TA, CYA and borates because of their tendency to have a negative effect on the CSI at the recommended levels in a salt water pool. One pool can have scale with a CH of 200 and another can be scale free with a CH of 1200; it would all depend of the pH, TA, temp, borates and CYA levels.

... not worth making generalizations like that IMO.

I am not interested in providing incorrect advice if I have done so. Please feel free to delete my posts in this thread

 

[jblizzle]

Brian, I was simply trying to point out that with the lack of information in the first post, jumping to "Your CH is fine" was a bit of a stretch and saying the high-ish CH would "benefit the SWG" did not make sense to me.

I think we are in agreement here that the CSI is what actually matters as far as scaling goes ... ignoring all of our ramblings