How much Borax to raise pH?

[chem geek]

Can tap water have high TA?

Yes it can. If your water is "hard", then it has high TA. Water hardness refers to the combination of both calcium and magnesium (and other minerals, but they are minor), but generally calcium is much larger in quantity than magnesium though this is dependent on the specific water source.

You can just test your tap water or you can look up the water hardness from your water utility district and then divide this number by 1.4 for a rough estimate of calcium hardness. The following table shows typical nomenclature for water hardness:

Soft 0-17.1 ppm 0-1 grains/gal
Slightly Hard 17.1-60 ppm 1-3.5 grains/gal
Moderately Hard 60-120 ppm 3.5-7.0 grains/gal
Hard 120-180 ppm 7.0-10.5 grains/gal
Very Hard 180+ ppm 10.5+ grains/gal

Some well waters can be well over 300 ppm in hardness. If the water source has passed through calcite rock (limestone), then it can pick up substantial calcium hardness since limestone is mostly calcium carbonate.

Richard

[mas985]

Check out my tap water:

City numbers
TA 225-276
CH 280-354
PH 7.9-8.0

Add a SWG and plaster pool, it is no wonder I use 1/2 gallon of acid a week.

[chem geek]

Wow, your water is very, very hard. You can try aerating your water (in a bucket or large tub) before adding it to your pool for refill since that will lower the TA. If you do that, you can add acid to it first which will lower the pH to make it easier to lower the TA (i.e. lower the pH and aerate according to Ben's alkalinity lowering procedure). Of course, if you just put in fill water through an automatic floater (similar to a toilet tank), then there's not much you can do except constantly fight the pH rise by adding acid.

The more troublesome quantity is the calcium since that will just keep getting added to your pool more and more. Eventually, you'll have to drain and refill substantial amounts of your pool water to get that down. Sorry you have such a difficult situation.

Richard

[mas985]

TA really has not been the issue since I need to lower PH so much. It pretty much stays 100-120 ppm. CH on the otherhand is a battle. Next winter I will do a refill when the city uses more surface water than well water and see if I cannot start out the season at 200 ppm. It does make me wish I had chosen a fiberglass pool though.

[Simmons99]

Well it worked - this morning PH is 7.5 and TA is 90.