TA question

swahl

Member
Jun 25, 2009
9
Chanhassen, MN
Not sure if "Just getting started" is the right place to post this; I'm in my 6th year of pool ownership, and
discovered TFP last year. However, it is my first post.

I've got a 29,000 gal vinyl sided pool, SWG for chlorine. I cannot thank you enough for the explanation of the relationship between CYA an FC (a nugget of info I've seen nowhere else) among other things! (And why the "superchlorinate" function on my SWG is not a substitute for shocking; the manual seems to hint that it is.)

My TA has always been high, it's running 180 - 150 at the moment. My son and I built a PVC aerator and I'm embarking on the lower PH + TA with acid, raise PH via aeration adventure.

My question is this. In the pool school section, it says:
If you have a SWG, or if you commonly run water features such as a spa, waterfall, or fountain, keep TA on the low side, between 60 and 80.
The salt water generator balance page simply says "this is IMPORTANT" without offering an explanation. I would like to know why it should be lower for a SWG! What happens if it is out of that range?

A second question I have, as long as you're reading this: Shocking the pool via the instructions on this site takes the pool to really high chlorine levels. What chlorine levels are too high to swim in? I'm guessing the answer takes the form of "Unsafe above x FC" or "Unsafe above y CC" or "Unsafe above z TC" or some combination of those. I looked but didn't find this info. Would a "when to consider it unsafe to swim in your pool" page be a good idea?
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,614
SW Indiana
The recommendation for lower TA in a SWCG pool is due to the natural pH rise caused by the operation of the SWCG. Higher TA also contributes to pH rise, so the combination of the two can make pH control difficult.
 

svenpup

LifeTime Supporter
Nov 18, 2009
835
Sacramento, CA
Chlorinating with an SWCG tends to cause pH to rise, as does high TA, so by keeping TA low you control the rate of pH rise.

Any FC level below "shock" level for a given CYA level is considered safe to swim in.

CC below .5 is safe, whereas CC above .5 indicates some sort of organic contamination, and the need to shock.