How much vinegar to lower PH?

[kervis]

So far so good with the new tub.  I have the temp set at 97 and the kids are in and out, using it like a pool as a few of you had mentioned they would--goggles and all!  I am pleased and proud that I have been able to keep up on the appropriate chems.    I've wiped a few invisible scum lines (could feel them).  Added Enzymes and no line this morning.  I am waiting for my Taylor kit to arrive. (Thanks Vinny and others!) I figure it will be a necessity as indeed this is being used like a small, warm summer pool at the moment.  I had to add more diclor in the middle of the day.   The colors on the strips look within range except for a high PH.  If I were to try to get that down without lowering TA, how much vinegar would I add to a 400 gallon tub? The strip shows pinkish dots, not even a solid color, that I figure is between the 8.0-8.4.  Otherwise everything else is progressing smoothly so far, due to all of your comments and experiences!

[Vinny]

Although I have used white vinegar to lower the PH (nothing to lower the PH and PH about 8.0), the amounts of chems needed for spas is relatively low. If you must use it I would start with about an ounce or 1 1/2 ounce wait a few hours and see how it measures.

The PH's stability is affected by the alkalinity. A normal alkalinity of 140 will be harder to change than a normal of 80. When you get the Taylor you'll see how many points the water is considered "balanced"

Also, a dose or two of MPS will sometimes bring the PH down again depending on the alkalinity.