Reduce Total Alkalinity Levels

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

no chlorine reading

Postby doug » Fri 07 Oct, 2016 04:31

if you are putting loads of chlorine in and getting zero reading you have chlorine lock often caused by over high levels of stabiliser usually cyanuric acid will require a water change up to 75% and future monitoring of cyanuric levels 30-50 ppm is ideal range more will reduce percentage of free chlorine and eventually lead to chlorine lock also chlorine dosing should be carefully measured not dump in by the shed load hope this helps


Re: Reduce Total Alkalinity Levels

Postby SteveO » Wed 14 Jun, 2017 17:03

Thanks for all of this helpful info. I came up with a cool way to aerate the pool. It used parts that many pool owners will have and it has been helping, so I figured I would share. I read that rain was good for aeration as the drops splashed on the surface. So, along those lines, I placed my pool cover pump into my pool and connected the output hose to a sprinkler that is spraying the pumped water back into the pool. The pumped water is getting aerated as it is sprayed, and the surface water is getting aerated as the water splashed down. Its bee running about an hour now and I can already see the bottom of the pool :D Hope this helps others.
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Re: Reduce Total Alkalinity Levels

Postby JillD » Wed 19 Jul, 2017 19:22

I Am jumping on this post As I can't figure out how to post a new post..... need help!!

I was suppose to put 4kg of alka plus in my pool and I put in 8kg! Was told by pool store to pt in whole bucket so I did then saw it was 8kg, I dumped in around pool all at once.... what can I do now? Just get it re-checked???
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Re: Reduce Total Alkalinity Levels

Postby JillD » Wed 19 Jul, 2017 20:16

My initial reading TA was 77
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Re: Reduce Total Alkalinity Levels

Postby Denniswiseman » Thu 20 Jul, 2017 16:52

If your pH is stable leave it alone
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Re: Reduce Total Alkalinity Levels

Postby GloriaFl » Fri 15 May, 2020 03:44

Larry wrote:The acid slug method in this post has been discussed and disproved throughout this thread. Here is a safer and better method for reducing Total Alkalinity written by Richard aka chem geek. Quoted in this post for easy reference.

The following method assumes 6.8 is the lowest measurement on your pH test kit:

StepAction to TakepHTANotes
1Add AcidlowerslowersAdd enough acid to bring pH down to 7.0
2AerationraisesnoneAerate until pH rises to 7.2
3Add AcidlowerslowersAdd acid to bring pH down to 7.0 (continue to aerate)
Aeration & Acid
nonelowersRepeat steps 1 & 2 until TA reaches the target
then AFTER you have reached your target TA
5AerationraisesnoneAerate until pH rises to your target (say, 7.5)
Net resultnonelowers

chem geek wrote:Neither the acid ball slug method nor the drizzling method are the same thing as lowering the pH significantly and then adding aeration while adding acid to keep the pH low. Even if the acid ball slug method is somewhat more effective at lowering TA (and this is controversial), it is not nearly as effective as low pH with aeration. This is the fastest way to lower TA -- guaranteed. It is the following procedure. Note that you should use the next to lowest measurement on your pH test kit as the low-end -- so if your pH kit only goes to 7.0, then use 7.2 as the low-end target and 7.4 as the high-end trigger to add acid to get back to 7.2.

ACTIVITY .......... pH .... TA ... The following assumes 6.8 is the lowest measurement on the pH test kit

Acid ..................... - ........ - ... Add enough acid to bring pH down to 7.0 (if it's already there, then just skip to the next step, aeration)

Aeration ............. + ....... 0 ... Aerate until pH rises to 7.2
Acid ..................... - ........ - ... Add enough acid to bring pH down from 7.2 to 7.0 (you may continue to aerate while you do this)
Aeration & Acid .. 0 ....... - ... Continue this combination (cycling of the two above) until TA is at the target you want

then AFTER you have reached your target TA,

Aeration .............. + ....... 0 ... Aerate until the pH rises to your target pH (say, 7.5).

Net of Above ....... 0 ........ -

Note that there is NO addition of base (Borax or otherwise) in the above procedure. Aeration would include running your SWG, running your waterfall, adding any fountains or other aeration features, getting an air compressor with a nozzle or pipe with small holes that produces tiny bubbles and putting that in the deep end of the pool, etc. By the way, rain is an excellent aerator with splashing drops, but unless you can control the weather...

The above procedure works because the rate of outgassing of carbon dioxide from a pool varies with pH and TA level and with aeration. Pools are intentionally over-carbonated -- that's why you initially add sodium bicarbonate / baking soda / Alkalinity Up on pool startup (unless your fill water is already high in Total Alkalinity). Think of the pool as a carbonated beverage -- it will outgas carbon dioxide. Stirring up (aerating) your drink causes more carbon dioxide to release faster. If you blow bubbles through a straw, the drink goes flat (loses its dissolved carbon dioxide) quite quickly. If you measured the pH and TA of your drink, you would find that as carbon dioxide is released, the pH rises with no change in TA. The same happens in a pool (for technical reasons I won't get into here).

This chart shows the relative carbon dioxide outgassing rate at various pH and TA levels. This is a relative rate since it is also a function of aeration, wind, etc. and that is not easily quantifiable. You can see how lower pH significantly increases outgassing. That's what makes the above procedure go faster, along with aeration. The outgassing rate also determines the amount of acid you would need to add over time to restore (lower) the pH. So running your pool at lower TA and higher pH will lessen the need for acid addition over time.

This chart shows the relative rate of pH rise at various pH and TA levels. Though the lower TA has a lower outgassing rate, it also has a lower pH buffering effect and these tend to cancel each other out though the outgassing effect is slightly stronger. This is why you can see some lowering the the pH rise at lower TA though running at a higher pH target is more effective (so most people do both -- lower their TA level AND target a higher pH).


This was the classic method, now debunked:

Here is a step by step guide to reduce the Total Alk of swimming pool water:
  1. Turn off the pump and wait at least half an hour for the pool water to stop moving.
  2. Choose an open spot in the deep end of the pool and pour the required amount of pH reducer slowly into this one spot. If you are using granule or powder pH reducer, first dissolve it in a bucket of water.
  3. The water will become hazy (like the heat coming off a hot road) and may bubble. This is normal.
  4. Allow the pH reducer to do its work for 20 - 30 minutes, then turn on the pump and circulate the water for at least 4-6 hours.
  5. Test again after 48 hours and repeat as necessary.
To find out how much pH reducer you need, you can use these handy Total Alkalinity Calculators. The calculators are metric and the conversions are:
1 gallon = 3.8 litres
1kg = 2.2 pounds
1 litre = 34 ounces

After giving the pool an "acid shock" like this, it is usual for the pH to drop. The high Total Alk causes the pH to rise again naturally, so wait several days after correcting the TA before adjusting the pH up. It is usually not necessary after the wait.

There are some who suggest that this method can harm some pool surfaces and they warn not to add more than 2.5 pounds of pH reducer for 10,000 gallons of pool water every 3-4 days. I regularly use up to 20 pounds for 10,000 gallons in one go and I have yet to have a problem. As long as the hardness level is at least 200ppm there is no reason for problems.

Comments and suggestions are welcome.

Hello! Thank you very much for this advice, it very helpful!

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