still having alkalinity problems

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
joeg

still having alkalinity problems

Postby joeg » Sat 14 Oct, 2006 10:27

Have read most of the postings and tried it - still no change - in fact worse! 20k gallon salt pool. Alkalinity 150 and ph 7.6. need to get to alk of 100. Have poured about 1/4 gallon a day in one spot after pump off for a while, waiting half hour and then ran for 5 hours. after a week of this, alk was 160! :( What am I doing wrong?


Flapoolguy
Pool Newbie
Pool Newbie
Posts: 5
Joined: Tue 15 May, 2007 19:53

Postby Flapoolguy » Wed 16 May, 2007 12:29

Is this a new pool? when my pool was new ph and ta was out of control due to the plaster cure.
me_too

Re: still having alkalinity problems

Postby me_too » Wed 16 May, 2007 21:17

joeg wrote:Have read most of the postings and tried it - still no change - in fact worse! 20k gallon salt pool. Alkalinity 150 and ph 7.6. need to get to alk of 100. Have poured about 1/4 gallon a day in one spot after pump off for a while, waiting half hour and then ran for 5 hours. after a week of this, alk was 160! :( What am I doing wrong?


Yeah that thing about pouring acid in a single column in the deep end to affect a change in the alkalinity without so much impacting pH doesn't really work well. It may have worked in a lab setting but in the real world there's just too much water for this to work.

Get your pH low, say 7.0, and constantly maintain it there (check often). If you have anything that disturbs the surface of the water (jets, fountain, whatever) turn 'em on. Keep adding acid to maintain the pH at 7.0, the alkalinity will drop. When you reach the desired level stop addind acid.

The secret to this recipe is to _maintain_ the pH at 7.0 all the time and turn on the fountain all the time. You'll need to check the pH often and correct it often but all is well.

For a small scale demonstration of what's going on, take a tablespoon of baking soda from the kitchen (that's your alk at 150) and pour some vinegar on it (that's your acid). Do this in the sink. The bubbles you'll see is the acid turning the alkalinity into carbon dioxide. (HCO3- + OH- -> H2O + CO2)

For a demonstration of why we're turning on the fountain, take a glass of Coke and stir it with a spoon, this increases the rate of outgassing of carbon dioxide. A few minutes of this and the Coke is flat.

It's the exact same thing we're doing with your pool, except the volumes are much different so it takes a few days.

Best regards,

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