Pool seems to like it's TA at 70

[BillyBumbler]

I add a few pounds of baking soda and without 7-10 days the TA creeps right back down to 70. It's a SWG pool and I add a bit of acid evey 3-4 days to keep the PH below 7.8, I figure the reason is that it;s a very new pool and also I hear the SWG pools generally have this maintenace issue of needing to add acid regularly and forever. But the TA at 70, should I keep after it or just let it go?

[Simmons99]

TA will reduce when you add acid - get PH down to 7.2-7.4, test an hour later, then add baking soda to raise the TA to around 100. See if that works.

I believe (but others can verify) that with the TA that low - it will allow your PH to bounce around (go higher) so that you have to add acid more than necessary, which reduces the TA.

Also - are you aerating your pool with your PH below 7.2? If so - it will cause your PH to raise and your TA to lower.

[chemistrydropout]

I have had the same experience as you on TA. Mine stays in the 70-80 range. Which is fine with me and my pool because the Ph stays at 7.5 almost religously. I like you have added soda to raise TA and it will come up to about 90 then settles back down to 70 in around a week. Basically all I add to my pool is bleach and some polyquat once a month. This is a IG 20x40 vinyl pool with no swg.
I contribute mine to having my returns pointed upwards to ripple the water. May or May not have anything to do with it. The pool tends to stay at a TA of 70 and a PH of 7.5. I have even changed the ph just to see what happens and it will settle back at these numbers given several days. That being said it is coming a gully-washer outside right now and I'm sure I will have to get everything straightened up this evening. It happens everytime I post something about a constant PH. I guess I should just keep my mouth shut!!!

[chem geek]

TA will reduce when you add acid - get PH down to 7.2-7.4, test an hour later, then add baking soda to raise the TA to around 100. See if that works.

I believe (but others can verify) that with the TA that low - it will allow your PH to bounce around (go higher) so that you have to add acid more than necessary, which reduces the TA.

Also - are you aerating your pool with your PH below 7.2? If so - it will cause your PH to raise and your TA to lower.

You shouldn't worry too much about your pH bouncing around even at a lower TA of 70. This is plenty of buffering unless you use Tri-Chlor tablets or MPS regularly since both are very acidic. The bottom line is that if you don't see much of a pH change (and you can measure the extremes in pH about an hour after you add chlorine and then again just before you add chlorine the next time) then you're fine.

A lower TA of 70 will let you maintain a lower pH or even a normal 7.4-7.5 pH much more comfortably with less pH drift. You can refer to this graph or this table to see how lower pH and higher TA lead to more outgassing of carbon dioxide which is what causes pH to rise in most pools. Exactly how much of a rise is dependent on aeration and that's something I can't predict nor put into graphs or tables!

Richard