how to Lower Alkalinity Help Please

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
cowladycc44

how to Lower Alkalinity Help Please

Postby cowladycc44 » Wed 01 Jul, 2009 07:39

The alkalinity in my pool keeps going up. The Ph is 7.6 stays the same but the alkanity keeps going up we have added 2 gallons of acid we have well water have added the metal free also and shock.
We bought the salt water system too now it said the salt is too high. So we are draining some of the pool to get that down and adding more water so now i guess i have to start all over adding acid am i right? What causes the alkalinity to keep going up help please.


chem geek
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how to Lower Alkalinity Help Please

Postby chem geek » Wed 01 Jul, 2009 09:50

Total Alkalinity (TA) usually only goes up from evaporation and refill since this adds to the pool water whatever is in the fill water. If the fill water is high in TA and Calcium Hardness (CH), then these will increase over time. If your pool is 4.5' deep and you have 1/4" daily evaporation, then this adds around 14% of your pool's volume in fill water every month. If the TA of the fill water were 200 ppm and your pool had 100 ppm TA initially, then this would increase the TA by 14 ppm every month.

However, it sounds like your TA is rising more rapidly than that so this could be from the chemicals you are adding. What is your source of chlorine? Are you using pH Up or Alkalinity Up products?
cowladycc44

how to Lower Alkalinity Help Please

Postby cowladycc44 » Wed 01 Jul, 2009 13:30

muric acid we added to get the alkalinity down they said sense we have well water it would take 14 oz of more acid then probaly 19 oz more after that and it would be three weeks before it goes down.
We have 0 chorline right now we are draning some of the water little at a time to get the salt level down before we add anything else to it. We drain a little then fill back with fresh well water. The bottom feels a little yuckey.
chem geek
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how to Lower Alkalinity Help Please

Postby chem geek » Wed 01 Jul, 2009 14:49

If you want to lower the Total Alkalnity (TA), the procedure is described in this post. Adding acid will lower the TA, but the process will take longer if you don't lower the pH more and aerate the water.

With a saltwater chlorine generator (SWG) pool it's a good idea to have the TA be lower (70-80 ppm) to minimize the pH rise associated with carbon dioxide outgassing that occurs faster at higher TA.
cowladycc44

how to Lower Alkalinity Help Please

Postby cowladycc44 » Wed 01 Jul, 2009 15:34

so no matter what i have to get the Ph down first then the alkalinity will come down then i bring back up the Ph am i right?
Does it hurt to swim in a pool that has High Alkalinity? Thanks for answering all my questions seems like the pool store should of told me to bring down the Ph first then the ta will come down but i think they like to sell more pool chemicals that way. Thanks again
chem geek
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how to Lower Alkalinity Help Please

Postby chem geek » Wed 01 Jul, 2009 21:34

Adding acid lowers the TA, period. It takes 25-1/2 fluid ounce of full-strength Muriatic Acid (31.45% Hydrochloric Acid) to lower the Total Alkalinity (TA) by 10 ppm in 10,000 gallons. The problem is that if you want to lower the TA by a lot, that the pH will drop too low. So you need to add acid to lower the TA, but don't go below 7.0 in pH. At that point, you want to get the pH back up so you can add more acid, but you should NOT add any sort of base (i.e. pH Up) to raise the pH or else you will just end up raising the TA again as well. This is where aeration comes in because it raises the pH with no change in TA. I hope this makes sense -- look at the table I linked to and see how this works.

It does not hurt to swim in a pool with high TA. There are only two issue with high TA. One is that it will tend to make the pH rise in the pool unless you are using an acidic source of chlorine (e.g. Trichlor). the other problem is that a pool with a combination of high pH, TA and CH can form scale.

As for the pool store, they just don't know any better since training in this industry is very poor and there are a lot of non-scientific methods people use that just aren't good or in some cases are untrue.
cowladycc44

how to Lower Alkalinity Help Please

Postby cowladycc44 » Thu 02 Jul, 2009 06:41

Thanks for your replys back to me going to give it a try. Thanks again cowladycc TEXAS
Sandi D in Saskatchewan

how to Lower Alkalinity Help Please

Postby Sandi D in Saskatchewan » Fri 13 Jul, 2012 17:49

How long do i have to wait to swim after adding acid?
chem geek
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how to Lower Alkalinity Help Please

Postby chem geek » Fri 13 Jul, 2012 20:51

With reasonable circulation, I'd say a half-hour is plenty of time, though in my own pool with good circulation I have no problem going in a few minutes because I add the acid (and most other concentrated chemicals) slowly over a return flow in the deep end with the pump running. I then lightly brush the side and bottom of the pool where I've added the chemical to ensure thorough mixing and to prevent pooling. Because I have floor drains in the deep end, it gets distributed very quickly. I've done chlorine tests where I measure most of the chlorine level in the entire pool within 10 minutes with no measurable change after 20 minutes.

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