how to fix zero pH

[laff66]

Our pool remodeler had to drop our ph way down to try to get some remaining scale off our pebble finish, and I am trying to get the pool usable quickly. My question is, will baking soda bring pH up immediately, or does it need to circulate for a while? I added about 11 boxes already and its still not even reading on my test kit that only goes down to 6.8.
The other question is what this is going to do to my TA which was fine before this. If it goes way up, will it come down at all, or will I have to drain and refill some of it.

 

[JasonLion]

Baking soda raises the total alkalinity quite a bit and only raises the PH a little. You want to use either borax or soda ask/washing soda to raise PH. Borax will raise the TA the least for a given amount of PH increase.

Since your TA is probably quite high at this point I suggest you aerate the pool as much as possible to bring the PH up. High TA and low PH and aeration will tend to cause the PH to rise without any increase in TA. You can aerate with spa jets, waterfall, fountain, rain, return aimed towards the surface, air compressor, etc.

 

[laff66]

Thanks for the quick reply. I can't believe I forgot about the third part of BBB. I remember reading that, but since the pH was always going up, I figured I'd never had to use it and forgot about it! Luckily I think our TA must have been really low, because after 11 boxes of baking soda the TA is only 40! We've had a ton of rain, so I'm guessing thats what caused it.
The pH is up to about 6.2 or so, but I have no idea how much borax to use! The bleach calc I have specifically says its not for borax.

Thanks again!

 

[JasonLion]

The general rule of thumb is that you need twice as much borax as soda ash/washing soda. But neither BleachCalc or my Pool Calculator is acurate when calculating PH changes at your extreme PH and TA. Both programs are based on smaller PH changes around a starting PH of 7.2 to 7.8 and a starting TA of 80 to 120. As you exceed those limits the amounts needed can be far greater or far smaller than calculated.

Using Chem Geek's Pool Equations, which does compensate for PH and TA extremes, I calculate that you will need on the order of three boxes of borax (228 oz) for each 10,000 gallons. But keep in mind that even that number is not exact. The actual amount will depend on what several of your other chemistry numbers are right now and how accurate the testing has been. You will want to add it in stages and retest after allowing each stage to circulate. That way you will be able to compensate for needing a bit less or a bit more than calculated.

As you add borax your TA will come up, ending up somewhere around 80, which is pretty good.

 

[giulietta1]

The general rule of thumb is that you need twice as much borax as dry acid.

I think you mean soda ash (washing soda) and not dry acid!!

 

[JasonLion]

I think you mean soda ash (washing soda) and not dry acid!!

Sigh, yes you are right. My mind is lagging behind my typing

 

[laff66]

My pH is almost up to normal, and the TA is still only about 40, so I should be getting close to okay. I've seen differing numbers on where my TA should be, though.

 

[JasonLion]

Congratulations!

Trust your tests and don't worry too much about the calculated values. I might do one retest just to be sure and then adjust things from there.