Lower Ph Without Affecting Ta

[mark0514]

Using a Taylor k-2106

My PH today is an 8, with 1 drop of acid demand. My TA is 90.

Do I need to lower my PH? If so, how could I withought lowering my TA? My water temp was 91.

I have a bit of a hard time with the CH test....as in when to stop counting, as the red turning to blue is really a matter of opinion. I had it down as 300, my pool store said 150. Today I would say 250.

Thanks

[chem geek]

You shouldn't worry about lowering your TA at the same time you lower the pH. If your pH tends to be too high, then your TA is too high as well. TA is not just a pH buffer but a SOURCE of rising pH in its own right, due to carbon dioxide outgassing. So just use acid to lower the pH and not worry about the TA getting lower. For spas getting dosed with hypochlorite sources of chlorine (such as bleach), the TA is usually kept lower to as low as 50 ppm if necessary. Since you are using a K-2106, I presume you are using bromine. Normally bromine tabs are acidic, but the same principle applies which is that if your pH tends to be rising, then lower your TA level.

For the CH, you are probably right in the 250-300 ppm range if that's where you saw the transition. Does your fill water have that high a CH or did you add too much calcium chloride to the spa? You should have around 120-150 ppm CH, mostly to prevent foaming.

[mark0514]

Thanks. That is my fill water CH.

[chem geek]

One more thing. Don't worry about the pH being up higher, especially with bromine since bromine is still very effective at higher pH. In order to reduce the chance of scaling, you can just keep your TA on the lower side in the 50-80 ppm range. If the pH is 7.8 or so, then don't worry about it. You shouldn't need to lower it below 7.6 (say, by adding acid if it hits 8.0).