New pool results

[chem geek]

Congratulations on your new pool!

Before taking any advice I give below, make sure you do what your pool builder says since this was a newly built pool. There may be some requirements for you to not violate the warranty of the build. Perhaps they want you to keep the pH or TA high during the curing process of the plaster/gunite (though my guess is that they don't).

The amount of acid it would take to lower the TA isn't something you can get from a kit. The kit will only tell you how much acid it will take to lower the pH (because the lowering of TA involves the outgassing of carbon dioxide and there is no way to accurately predict that since it is a function of aeration in addition to pH and TA level). To lower the TA, you need to follow Ben's Lowering Your Alkalinity procedure which involves adding acid to lower the pH significantly (to around 7.0 or so), then aerating the water while adding acid to keep the pH low, then when the desired TA is reached, stop adding acid and keep aerating until the pH rises to the desired level. Again, check with your pool builder since they may not want you making the water that neutral so soon after a new plastering. If they don't, then you can just add acid to get the pH moderately down to their recommended level, but you'll be adding acid frequently and the pH will keep wanting to rise (Ben's procedure uses the same amount of total acid, so it's a lot of acid, but accelerates the process so you lower the TA much more quickly).

Until you get your TA down, it will be difficult for you to maintain a normal pH. The fact that it is a new gunite pool means that the plaster/gunite is still curing and that will cause the pH to rise significantly anyway so you can expect to be adding acid regularly for a while even after you get your TA lowered. However, right now having the TA so high just makes it that much more difficult to get the pH down and has you using that much more acid so I suggest following the procedure above.

By the way, if your Pentair test kit doesn't also test for Calcium Hardness (CH) or for Cyanuric Acid (CYA), then you should get a better test kit such as the Taylor K-2006 which has those additional tests (and also has an accurate drop-based FAS-DPD chlorine test and of course a Total Alkalinity test). It would be interesting to see what your Calcium Hardness level is since the high TA and pH are almost to the point of causing scaling, but perhaps with the new pool build they have the calcium on the low side since calcium hydroxide is expected to be introduced into the pool through the curing of the plaster/gunite.

Why is your target TA 120 ppm? Usually that high a TA is only needed if you plan on using an acidic source of chlorine, such as Trichlor tablets. Otherwise, if you plan on using chlorinating liquid or bleach, a TA of 80 to 100 ppm is usually more appropriate (80 ppm is better if you have aeration features or otherwise find that your pH tends to rise).

Richard