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 (http://richardfalk.home.comcast.net/pool/CO2.png) or this table (http://richardfalk.home.comcast.net/pool/CO2.htm) 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