Somewhat Confused With CSI and TF Recommended Balance W/ SWG

[Duk]

I am somewhat confused about the recommended TF balance for a plaster pool w/ SWG and the resulting CSI values. My current test results are as follows;
pH- 7.5
FC- 10
TA-60
CH-375
CYA- 75
Borate-20
Salt-3200
Temp- 81 deg.
CSI- (-.48)

I know I'm slightly on the high side with my CH values but it is not significantly high and will come back down if it ever rains again here in Houston. I lowered my Ta to 60 recently to try and help stabilize the pH which has done. But now I have these rather high negative CSI values. If I lower the CH it only gets worse, but I would be within the recommended balance for a plaster pool with SWG. I do not want to etch my plaster and it seems I would be better to let my pH rise up to 7.8 to 7.9 and I would be at a more conservative balance. Am I interpreting the Pool Calculator correctly or am I missing something here? It also seems I would be better off to let the TA rise to about 80 and live with the fluctuating pH which is what I have done in the past. It just takes alot of MA to keep the pH below 8.0. I apprereciate your advice and thoughts.
Larry

Note- I'm letting the borate levels dilute due to our dog Gator, who loves to swim with us.

 

[Bama Rambler]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

People tend to put too much truck in the CSI. Don't worry about it till it gets significantly past .6 one way or the other. Just by letting your pH raise a little it changes it.

 

[Duk]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

So if I read you correctly, I don't need to worry about any long term effects to my plaster as long as I am between -.6 to .6?
Thanks for the fast feedback!
Larry

 

[JasonLion]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

As Bama said, CSI isn't a big deal in this range. Letting PH go up to around 7.7 or 7.8 is fine. Raising TA is not a good idea, as that will make the PH less stable.

 

[Duk]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

Thanks Guys!

 

[donaldm823]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

I hope you get answers that say -.44 is OK since the low spec is -.6. I frequently get numbers like -.44 the day after an acid add (I add to 7.5), then the pH rises over the next 5-6 days to 7.8 (and the CSI rises corresponding) when I add another 48oz of acid.

My other pool chemistry program calculates a -.19 since it corrects for the CYA contribution to your TA

 

[Duk]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

I did not know that the CYA value contributed to the TA value. Learned somthing new !
Thanks,
Larry

 

[JasonLion]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

The Pool Calculator corrects for the CYA contribution to TA, and several other factors not accounted for in LSI. It is the most precise tool available. Most other systems use LSI, which is a simplified system designed to be easy for people to calculate, rather than being precise.

 

[HouTex]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

"I do not want to etch my plaster and it seems I would be better to let my pH rise up to 7.8 to 7.9 and I would be at a more conservative balance. "

Duk, I had similar readings as yours (but with contantly rising pH--I have a new pool) but with the drought here in Houston and with 150 CH fill water (in the Memorial area) my CH went up to 675 in just six months from the initial fill. With the pH hitting 8.2 for perhaps one out of four days (I would add MA to bring it back down to 7.2) I developed scale on my plaster. Part of the problem was that two pool stores said my CH was in the 400 range and even with pH at 8.2 the CSI at the time (I thought) was around zero so I wasn't concerned. Now I'm very careful to keep pH at or below 7.5 and to watch my CH very carefully. And never trust the pool store's tests.

 

[Duk]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

No doubt Jason, it is a great tool and I use it all the time. We really appreciate all you do for this forum. There is no way I could quantify all the dollars saved in preventing potential damage, maintenance and wasted chemicals and the pool knowledge I've gained over the years on this site from you and the other moderators and contributors.
Thanks Again,
Larry

 

[Duk]

Re: Somewhat Confused With CSI and TF Recommended Balance W/

"I do not want to etch my plaster and it seems I would be better to let my pH rise up to 7.8 to 7.9 and I would be at a more conservative balance. "

Duk, I had similar readings as yours (but with contantly rising pH--I have a new pool) but with the drought here in Houston and with 150 CH fill water (in the Memorial area) my CH went up to 675 in just six months from the initial fill. With the pH hitting 8.2 for perhaps one out of four days (I would add MA to bring it back down to 7.2) I developed scale on my plaster. Part of the problem was that two pool stores said my CH was in the 400 range and even with pH at 8.2 the CSI at the time (I thought) was around zero so I wasn't concerned. Now I'm very careful to keep pH at or below 7.5 and to watch my CH very carefully. And never trust the pool store's tests.

You are so right. I learned this lesson the hard way several years ago. It was what converted me to a BBB guy. I don't trust much of anything I hear at the pool stores.
Larry