3rd Week with new pool

[bumpy1]

This is our 3rd week with our new (1 year old pool) that came along with a new home purchase. Test #'s looked inline the first time I tested, albeit with low salt (2,000 ppm). Dumped 140lbs of salt in approximately 3 weeks ago.

Decided to retest (using the local pool store while I wait for a tes kit). Numbers look like the following as of today:
TC: 3
FC: 3
pH: 8.1
TA: 140
CYA: 50
Salt: 3140
Calcium/Hardness: 250

Water is crystal clear.

Pool is 29,700 Gallons, Gas Heated (Sta-Rite Max--Therm 400HD), SWG (Pool Pilot DIG-220), Filter (Sta-Rite S7M120)

Concerned about high pH and looking for direction. Been making my way through pool school and not ready to be out on my own.

Thanks in advance.

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[JamesW]

Very nice looking pool.

The high pH is being caused by the high TA (Total Alkalinity). When lowering TA, you lower the pH to 7.2 until the TA gets down to the desired level (about 60 to 70 ppm), and then you keep the pH at about 7.6 to 7.8.

You can use the pool calculator to calculate amounts of chemicals needed to adjust chemical levels.

pool-school/lowering%20total%20alkalinity

 

[woodyp]

Pick up a gallon of muriatic acid and dose it down to 7.2 or so according to the pool calculator for your gallons. Probably around a half gallon or a little less.

 

[bumpy1]

Thanks. Pool calc indicates 116 oz's of 31.45% 20 Baume MA or Dry acid @ 156 oz by weight or 104 oz by volume. This said, Pool Calc mentions a pretty significant caveat: "Results are approximate and can be off significantly for large pH changes."

Is a change in pH of .9 significant ? Can I rely on these #'s ?

 

[JamesW]

Start out with 64 ounces (2 quarts) of 31.45 % muriatic acid and retest in one hour. Pour the acid slowly into the return stream to allow it to distribute evenly. Make sure that the wind is blowing from you to the acid to avoid getting the acid fumes on you.

It's probably going to take a total of about 4 gallons total to get your TA down to 70 ppm. There really is no hurry, just keep adding the acid as needed to keep the pH down to about 7.2 to 7.4 until the TA eventually gets down to about 60 to 70.

 

[bumpy1]

So I guess I'm a little confused. Please bare with the newbie. Pool calc indicates 116 oz, your saying I will likely need over 4 times that amount ?

 

[JamesW]

The total alkalinity needs to be lowered in stages. Every quart will lower the TA by about 4.2 ppm. To lower it by 70 ppm, you need to add a little over 16 quarts (4 gallons). However, it is not safe to add this much acid at once because it would cause your pH to go too low.

You only add enough acid to lower the pH to not lower than 7.2 and then you wait for it to rise again. This process will take days to weeks. When you lower the pH, it will take anywhere from 1 to 7 days to rise back up enough again for you to add more acid.

Mostly, just keep adding acid as needed to keep the pH between 7.2 and 7.5, and you will be fine.

pool-school/lowering%20total%20alkalinity

 

[bumpy1]

Ok. Thanks. BTW, PS kid told me I could pump 2 inches of water to waste and refill to drop the pH as well. Is this a plausable solution ?

 

[JamesW]

No, that won't work. The pH and TA would have to be very low for that to work. No fill water is going to be that acidic.

What are the numbers on your fill water?

pH, TA and calcium hardness?

 

[Melt In The Sun]

Don't worry about your TA right this moment. It is just not that critical.

Pumping water out won't work, as James said.

The pool calculator relies on certain assumption when it calculates the amount of acid needed; the most important (and most likely to be wrong) is the size of the pool. So, add maybe half what it says you need, get another test, and then put your new numbers in the calculator and do the whole thing again. It will be much easier once you get your own kit!

Again, ignore TA for right now. You can fiddle with it later if you want to.