Upwardly drifting PH...


New member
Dec 9, 2014
Tacoma area, WA
Hi there! I recently revived my 425 AG Sierra 6000 spa and have been going nuts keeping the PH level down... here's my current test as of 20 minutes ago:

FC - 4
CC - 0
pH - 8.0 (just added 1 oz of sodium bisulfate - 2 drops on acid demand test)
TA - 70
CH - 170
CYA - less than 30 - filled up the comparator and could still see the black dot.
Borates - added Gentle Spa per its instructions. Unknown how much is in there and I don't have a test for it.

The water is clear and smells just fine. I arrived at those numbers based on the recommended pool calculator values. I've been noticing since I filled the spa that the PH drifts to 8 and stays there. It is always a 2-drop acid demand per the Taylor K-2006. I'm constantly having to add "PH Down" to come down to 7.4-7.6 levels.

I have a Nature2 mineral filter that is not installed and the filters (microfiber sock-style) are brand new and clean. I've been trying to find a cartridge conversion for that, by the way... but the holes are not threaded. Unicel told me I'm SOL.

The spa is always covered and only exposed to the elements when we are in it.

Anything stand out?

Thanks in advance!

- Jordan


LifeTime Supporter
Platinum Supporter
TFP Expert
May 7, 2007
Silver Spring, MD
Welcome to TFP!

Your TA is too high. Lower TA to somewhere around 30 to 50, what you really want is the highest level where the PH is stable and you should be good.


New member
Jan 3, 2015
I have the same problem as Jordan with an indoor spa... Appreciate your advice to keep TA in 30 - 50 range which is where it wants to "stay" BUT health department says it needs to be minimum of 70. Consequently I am always fighting high PH and low TA (since I have to maintain at least 70...)

chem geek

LifeTime Supporter
TFP Expert
Mar 28, 2007
San Rafael, CA USA
Welcome to TFP! :wave:

By "health department" I presume you are referring to a commercial/public spa? Otherwise, you can do whatever you want with your own residential spa.

If the spa is commercial/public and if the health department requires a minimum of 70 ppm TA, then with aeration from jets, splashing, etc. you are going to get pH rise. The pH will rise less and use less acid at higher pH than at lower pH but here again your health department may limit how high your pH can be. At any rate, don't try and lower the pH below 7.5 and if you can target 7.7 or 7.8 it will give you less grief. You will, however, need to add acid frequently, or can add carbon dioxide if you decide to go that route. Technically, adding acid will also lower the TA so to maintain 70 ppm you will be in the vicious cycle of adding both acid and bicarbonate. Since most of the pH rise is likely due to carbon dioxide outgassing, it would be better to simply add carbon dioxide back into the water so you won't need to add baking soda to maintain the TA. Of course, having a lower TA lessens the need even for carbon dioxide, but that's not an option for you (thank you health department that doesn't understand water chemistry).

You might be interested in the short Ted-talk-style presentation I gave at the last World Aquatic Health Conference on Reducing Facilities Chemical Costs By Proper Management of Total Alkalinity (TA) and pH.


TFP Expert
Feb 3, 2014
Central Minnesota
Loved the slideshow chem geek! It's a great look at how TA affects pH rise and for the commercial folks, how it can be manipulated to reduce costs... if the regulations allow it.


LifeTime Supporter
TFP Expert
Apr 14, 2011
Murrieta, CA
Nice slide show. Great info. I know about CO2 lowering PH. I did "Dry Ice" in my pool one Halloween Party. It was very cool. My pH dropped. Think I used about 15 lbs or so during the evening.


New member
Dec 9, 2014
Tacoma area, WA
Thanks for the responses! I, too, was confused by the "lower your TA" remark. I was going off several different sources who said the the "minimum" TA is 70 ppm... I had read that elevated TA caused pH rise so that's why I dialed it in at the lower end of the "recommended" TA spectrum. I guess it's still too high.

You guys are awesome. I'll drop it down and see if that fixes things.