Reduce Total Alkalinity Levels

[Johnny Tikinut]

Hey Chem Geek,

Your advice is awesome. I recently drained my pool here in southern California due to high cyanuric acid. After completely draining and refilling the pool my PH was beautiful at 7.5, however my alkaline was about 175-180 (the test "pinked up" at 170 & went red at 180). The guys at my local pool store and much of the online advice suggested no more than 2 cups of Muriatic acid for 10,000 gallons. They also generally advised to wait 3 days to add more acid. After nine days of struggle I managed to drop the alkaline a whopping 10 PPM. Then I found your advice about adding acid and bottoming out the PH, then bringing the PH back up (chemical free) through aeration. In 5 days I have brought my PH down 45 PPM. I am now at the top of the recommended 80 - 120 range squarely at 120, and plan to be at my goal (100) by tomorrow night.

On another site I found some very interesting designs for aerators using the pool returns. I had tried the compressor method but found it to be too loud for me and my neighbors. The return in my pool was the same size as the one in the aerator example 1 1/2 inch (perhaps that is standard). I picked up a threaded male to female PVC piece that screws into the return. From there you would use a short piece of PVC - 3 or 4 inch - just enough to fit on a 45 degree elbow. From there you would use a piece of PVC long enough to get you a little under a foot above water level. On the sample I worked from the author then had a 90 degree elbow so the water would shoot back with force at the water surface. In my case I didn't feel my pressure was strong enough to warrant the elbow, so my water shoots up and the falls a bit harder on the surface. Either way you finish the design off with a 1 1/2 inch PVC cap that you must drill holes through. The internet version drilled 4 holes at 7/16, but I opted to go 8 holes at 7/32. When I made a second one for the other return I wanted to try to increase pressure so I only drilled 5 holes at 7/32. Either design made a nice aeration effect, seemingly without disrupting flow.

Using these two aerators I found that I could add two cups of acid in the morning and two again in the evening without going below 7.2 PH. My apologies up front if you have already addressed this aerator method, and I won't give a site name for what may be a competing website; however for those of you who require pictures to work from I'm sure a little Google creativity will get you there.

Thank you so much Chem Geek. I think it is great that someone living halfway across the state from me would take the time to post information that is valuable, yet free, for so many of us to benefit from.

Thanks,

Johnny

[Johnny Tikinut]

In my previous post I said "In 5 days I have brought my PH down 45 PPM." I meant to say that I brought my alkaline down 45 ppm.

[chem geek]

This site does not ban you for linking to other sites if the information is useful and relevant. The Lowering Your Alkalinity post at TFP has links to 3 different styles of home-made aerators plus one that brings in air like a spa. I'm glad the method, based on known chemistry/physics, worked for you.

[Allen G Myerson]

I recently drained my pool here in southern California due to high cyanuric acid. After completely draining and refilling the pool my PH was beautiful at 7.5, however my alkaline was about 175-180 (the test "pinked up" at 170 & went red at 180).

There is a service in Southern California that uses commercial reverse osmosis filtration to lower unwanted dissolved solids, such as cyanuric acid. It can be a good option in many cases.

[Johnny Tikinut]

Thanks again to the contributors here. Richard - after reading your reply I realized that I probably got the link to the aerator's from here in the first place. I just followed your latest link "Lowering your alkalinity" on TFP. I'm curious what the theory is about not lowering your alkaline just to reach a target number. I'm pretty sure that's exactly what I just did. I brought my alkaline down from about 180 to 100 because the paperwork with my test kit showed the ideal range to be 80 - 120, so I thought that I would go up the middle. So now I am curious as to why this is not the right thing to do, can you clarify?

[Allen G Myerson]

Then I found your advice about adding acid and bottoming out the PH, then bringing the PH back up (chemical free) through aeration.

The reason that aeration raises the pH is that it forces some of the carbon dioxide in the water to go from being aqueous (dissolved) to a gas that is not dissolved, which it lost to the air. Loss of carbon dioxide raises pH. Adding carbon dioxide back into the water lowers the pH.

Since the water is oversaturated with carbon dioxide, carbon dioxide will be lost on a continuous rate. The rate of carbon dioxide loss is determined by several factors, including water temperature, aeration, pH and alkalinity. By controlling these factors, you can increase or decrease the loss rate, and the resulting rate of pH rise.

You need to adjust the rate of pH rise due to carbon dioxide loss to match other factors that affect the pH, such as chemical additions etc.

For example, when you use acidic sources of chlorine, you want to increase the loss of carbon dioxide, by increasing the total alkalinity. When you are using more basic chlorine sources, such as hypochlorite, you want to decrease the carbon dioxide loss rate.

.....Factor.......................................Effect

Higher Alkalinity............ Faster carbon dioxide loss rate
Hotter water................ Faster carbon dioxide loss rate
Aeration......................Faster carbon dioxide loss rate
Higher pH.....................Slower carbon dioxide loss

[chem geek]

With regard to the TA and pH levels and how they affect the carbon dioxide outgassing rate, this table shows how much more carbon dioxide there is in the water than there would be at equilibrium with the air. You can see how pH and TA are big factors. In fact, the rate of outgassing varies with TA more than shown in the table since it apparently varies with the square of the TA based on experiments by John Wojtowicz.

[lostscouse]

My total alkalinity is of the scale and have tried pH minus to reduce this and also TA reducer- both recomended by a local pool guy. Nothing seems to be changing. 14,000 gall pool. water supply that filled the pool also giving the same readings. Help???

[Michael K]

United Chemical makes a product called "Easy Acid", it is a powder that is said to lower TA strongly and only lower PH moderately. Is anyone familiar with this product? I have tried using a compressor in the deep end of my pool and let it bubble for hours with absolutely no change in TA. I have used the slug method and brought my TA down from 230 to 120. Does any place sell an aerator that will lower TA?

[chem geek]

That is just a bunch of bunk. Acid lowers both pH and TA. Aeration just raises pH without raising TA. So the combination lowers TA faster -- if you lower the pool's pH more and aerate more then the TA will drop faster, but it takes the same amount of acid to lower it regardless. The slug method doesn't lower TA any more than any other method of adding acid. If you add 25-1/2 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) to 10,000 gallons, it will lower the TA by 10 ppm. It doesn't matter how you add it, the same TA drop will result. What WILL be different depending on how you add it is the amount of damage you do to your pool by slugging it -- if the acid pools near the bottom it can dissolve plaster or thin/weaken/fade vinyl.

See this paper for more technical and experimental info.

[Guest]

OK, I am a first time pool owner. I had beautifully clear water until I got over zealous and bought into the line of crap that Arm & Hammer used to sell me their "Clear Balance" tabs. Now I have cloudy pool water, due to high pH and TA. After doing research and realizing it's totally my fault (their tabs are mostly sodium bicarbonate), is using acid the only thing I can do? I'm a little nervous about using it in my cheapo Wal-Mart special vinyl-liner pool. Will it damage it if I don't do it right? And as for the aeration, is turning the return upwards enough? Could I turn a garden hose on over the surface and let it sprinkle? Can we swim in it after adding acid? I have a bunch of questions and am totally frustrated....

[chem geek]

You can use Muriatic Acid, but just pour slowly over a return flow with the pump running and then lightly brush the side and bottom of your pool where you added the acid to ensure thorough mixing. Just don't let our pH get below 7.0 and you should be fine. You can point your returns upwards and run the pump on high to improve aeration. You can swim and splash as well (wait 10 minutes or so before going into the pool, assuming you've got good circulation -- 30 minutes if your circulation isn't as good). When the pH goes up to 7.2 (or more), add acid to bring it back down to 7.0. The procedure is described in this post.

[stmscelcajon]

Our pool is about 100,000 gallons and is 3 foot to 5 foot in depth 6 x 25 yard lanes. We are a teaching and therapy pool and the water is kept at 85 to 86 degrees F. year-round. We just had our pool chemistry checked by the pool service and they told us that we are at 7500 ppm total dissolved solids. Calcium hardness is very high. We were told that there may be a service that has a mobile filtering system (Reverse Osmosis I guess) that can come to the pool and suck the water out filter it and put it back in the pool. We are wondering if anyone has heard of such a service and if you have any other solutions besides dumping all the water down the sewer system. We are not liking the idea of wasting all that water here in So Cal not to mention the cost of buying 100,000 gallons of new tap water. Any ideas are welcome. Thank you .

[chem geek]

Reverse Osmosis (RO) is very effective but is not available in all areas. It's an effective way to reduce everything that is in large concentration in the water, not only TDS (which is mostly salt), but also CH, TA and CYA. Is your quote from Pool Services Technologies, Inc.? If so, they have done a good job for many pools and you can, of course, get references from them if you desire.

[haskins200]

Larry,

I have this problem: Muriatic acid versus liquid shock

Postby haskins200 » Mon 15 Jul, 2013 20:49

I am torn between using either muriatic acid or just putting liquid shock in my pool. I have an above ground 24 ft. round pool with a cartridge filter pump. I can't manage both the ph and alkalinity. It is so cloudy you can't see 2 ft. in front of you. I was told to shock it with liquid shock, but then I was told to add this other type of acid? Both the ph and alk is high! I have shocked my pool twice since spring.

So should I just shock it or add the acid? And, I was told by pool experts than you can enter your pool 1 hour after liquid shocking it? True or false?

Thanks for any input.