Alkalinity @ 50ppm

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Fireman John

0
Dec 8, 2017
10
Athens GA
I am new to the forum, so if this thread is in the wrong place, or has been answered somewhere else, please forgive . I will figure it out. My question is on the Pool Math calculator. My alkalinity has maintained all summer around 60, and currently is 50 on 12/08/17. PH has maintained around 7.6-7.8, and is currently 7.6. Based on the trouble free calculations/pool math, alkalinity should be 50 to 90+, but keep reading elsewhere on other pool sites, that alkalinity below 80 will hurt my vinyl lined pool. Everything seems fine. Water is clear and not irritable to swim in, or was. Currently covered with loop-loc safety cover, but operational . I thought to high or low PH is what causes problems. Anyway, can someone shed some light on this? Should I be concerned with alkalinity at 50-60 or should a raise it? Thanks

12/08/17 Taylor FAS-DPD comlete test kit.
PH 7.6
Alk. 50
calcium 150
CYA 25
FC 6
CC 0
 
Your pool is fine. TA recommendations from the industry range from 80-120ppm but that is based on a complete misunderstanding of what alkalinity is and what is does. The industry (and most junk you read on the internet) is simply wrong from a scientific standpoint. Your vinyl liner is completely immune to alkalinity. pH is the main driver of any type of "corrosive" issues and a vinyl liner can handle pH values well outside what is normally found in pools (both very acidic and very alkaline pH values). As long as your TA is a bove 50ppm and your pH remains stable, there is no reason to adjust it.
 
Matt thanks and I agree. I have some understanding of chemistry thru Haz Mat classes at the fire dept., but being I am a new pool owner, just wanted to make sure I was not misunderstanding something (alkalinity) when it came to vinyl lined pools. In the beginning I tried to keep alkalinity around 80 and kept fighting the PH (high). Once I found this site I let the alkalinity drop based on the pool math, things seem to stabilize.
 
Welcome Fireman John and thank you for your service to your community!

When using PoolMath attention should be paid to the calculated CSI value.

Using your numbers and the following guesses:
SALT 1000 (somewhat typical in non-SWG pool)
Borate 0
Temp 60

PoolMath is showing your pool with a CSI of -0.74. It is recommended to keep this between -0.6 and +0.6. A rise of pH to 7.8 will yield a CSI of -0.55. If the pH is stable at 7.6 you could consider adding a bit of Calcium to get it up to around 250 yielding a CSI of -0.53. Unfortunately, the CSI goes more negative as the water temp drops so you are fighting that this time of year.

I am assuming you are using either a SWG or liquid bleach/chlorine as your CYA is only at 25 (which by the way would be rounded up to 30). If SWG then your SALT will be much higher than assumed above (and CYA should be in the 70-90 range).

I am only regurgitating what I have learned from TFP. The TFP experts are welcome to chime in to correct my logic or let you know that your current CYA through the winter is OK. I am an engineer and if the spec says -0.6 to +0.6 by golly that is where my pool is! :geek:
 
The OP has a vinyl pool, CSI is not very relevant. His CH is at the low end for vinyl but OK. I would bump up the CYA to 30-40, keep the FC in the right range and leave everything else alone.
 
As this is a vinyl lined pool, CSI is not a critical value to monitor as long as the rest of the chemistry values are kept in the recommended range.

Take care.
 
Thanks everyone for your responses. It has been my understanding that calcium levels and CSI are not very relevant with a vinyl lined pool unless way out of range. i.e. calcium way high. That's why I posted about alkalinity. Did not want something that was hurting my liner that I was not aware of. Correct me if wrong. I usually keep CYA around 30, but I have had a good bit of rain so it has dropped a little. I said CYA 25, but probably somewhere between 25-30. I have my pool covered with a safety cover loop-loc, not solid (green) so I have not been really concerned about CYA as the pool is not getting any direct sun. Will adjust when I open in the spring. My main attention is to keep PH and FC in range. Will bump up FC. I use liquid chlorine. I run the pump a couple of times a month just to filter and turn the water over at least once. Got it running now though as metro Atlanta area getting cold weather.
 
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