Rookie mistake after adding Borates....advice needed

[glo76]

Bit reluctant to admit a rookie mistake in a Chemistry 201 forum....but here goes. Last couple of weeks I've been progressively lowering my TA to prepare to add borates. pH has been stable for a week with a TA of 60 so on Saturday I added the 38 lbs of boric acid required to get my pool to 0.5 ppm. About 4 hrs later my pH had fallen from 7.5 down to 7.2 which running through Pool Math made my CSI drop to -0.66 suggesting corrosion of plaster. No problem I thought, just adjust the pH....but for some reason I stupidly read 'washing soda' to mean 'baking soda'. Now my TA is back up at 90 after all that work getting it down to 60 where I wanted it.

I'm looking for advice on next steps. I'm sure my TA is going to be too high and I'll see pH drift upwards (negating one of the reasons why I added borates in the first place). Should I leave TA where it is, just monitor, and accept that I'll need to keep adding MA? Or try to lower TA through lowering pH and aerating? Lowering pH to 7.0 will put my CSI <-0.6 again....but only for a short period until pH comes back up again. Is that ok?

Current readings as of Sunday evening:

FC 13
pH 7.6
TA 90
CH 300
CYA 50
Salt 1700
Borates 50
Temp 84
CSI -0.08

 

[Donldson]

With an FC of 13 your pH reading is suspect, so I wouldn't do any adjusting yet. Retest it after your FC is below 10. As for your TA, yes you will see your pH rise slowly, but the borates will slow that rise considerably. I would just test regularly and dose as needed, rather than actively attack it. You should find the problem is not as bad as you think it will be.

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[JoyfulNoise]

It's fine. You can still lower your TA, it just takes more acid than before the borates to do it. There's really no problem at all.

Also, just a note about CSI - when your CSI is -0.6 and the warning says that it's corrosive to plaster, it's really not an imminent problem. Pool water CSI values really need to be less than -1.0 for there to be any real problem and even then it would have to be a sustained negative value for a long time (we're talking weeks or months) for you to notice anything substantial. So you take the warning at -0.6 as an advisement to rebalance your water. In reality, you could have done nothing and your pH would have come back up on its own naturally and the CSI value would have been fine.

 

[glo76]

Thanks guys - good advice. I'd forgotten about pH reliability with FC>10. I now realize I was very hasty in trying to adjust my pH and could probably have left it, kicking myself about that. I'll monitor and see how it goes.

 

[camueller]

Just to add, I did the borate thing and after adding them plus filling up a bit with high TA water, I found myself back up to 90 TA. I didn't worry about it. It took weeks before my pH ever moved, and so far it's only gone up from 7.5 to 7.6. My TA is back down to 70 now after a lot of rain and draining, but things have been smooth sailing overall. Don't worry about it, just get the FC level down below 10 and then adjust pH.

 

[glo76]

Thanks camueller. Sounds like I may be worrying a bit too much about this.