Reducing Alkalinity while maintaining PH using Muriatic Acid and Borax

J03

New member
Jul 27, 2020
2
Southern California
Hello All,

I bought a new home last summer with a salt water pool and I've really dived into the pool maintenance thing since. I bought a K-2006 Salt test kit and with the help of this forum and the calculator, keeping my levels have been relatively pain free with the exception of my Alkalinity levels which have been plaguing me since day one. Since I bought the house late in the pool season I just put off dealing with it until this spring because at the start of this pool season I was going to try introducing borates into my system and figured at that point I could utilize the Borax to achieve what I needed. When I reopened the pool I found some of my levels were off so I have some other things to take care of as well but I wanted to tackle one thing at a time. Specifically my CYA has dropped to 50 from last seasons 80. I assumed this would only affect my chlorine levels so I haven't gotten around to bringing that back up yet but if that could be affecting it please let me know. Back to my efforts...

Starting:
PH: 7.4
TA: 140

My understanding from doing research is that Borax will raise PH without raising Alkalinity so the idea is to bring the PH and Alkalinity levels down and then just raise the PH back up with Borax, rinse and repeat so PH doesn't get dangerously low. I went ahead and bought a few jugs of Muriatic Acid as I had just run out and several boxes of Borax to start. I wanted to do a test run of this before I cleaned out the store of Borax, especially because it would be harder to lower my PH after the borate levels were up. I added enough Muriatic Acid to bring down the PH to below 7 on the test kit (added enough to sit around 6.8) which also brought down my Alkalinity levels down to ~125.

After Muriatic Acid:
PH: 6.8
TA: 125

I then went ahead and added a couple boxes of Borax and waited a day to test again. I just tested the water now and that's what triggered this thread. The levels for both are right back to where I started.

After Borax:
PH: 7.4
TA: 140

I feel like I'm back to square one. I know I haven't provided all of the figures for my pool here but I thought these were the relevant ones for this particular discussion.

Thanks for any advice you may have. My understanding is that aerating the pool is another option for raising PH without raising Alkalinity but I wanted to introduce borates into my pool anyway so I thought the Borax route was my best bet.
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Welcome to TFP! :wave: So I'd say a few things about your TA questions. First, Borax is fine to increase pH when needed, but it does influence TA a little. The best way to increase pH with NO influence to TA is aeration. The more aeration you can create the faster the pH will rise.

About the TA itself..... while 120-140 may be a bit elevated, it's not crazy high and not something you have to attack too aggressively right now as long as you control the pH. PH is always more important because it has the most significant influence on your overall chemistry.

So next time you decide to try and lower TA, use the acid to lower the pH to about 7.0, then simply create aeration until the pH gets up to about 8.0 - then repeat. But if the pH is remaining stable in the 7.6-7.8 range, there is no need to beat yourself up with TA. Just leave it alone.

Don't forget to sign up for our PoolMath APP which is a great tool. Also update your signature with all of your pool and equipment details. It will help later.
 

J03

New member
Jul 27, 2020
2
Southern California
Welcome to TFP! :wave: So I'd say a few things about your TA questions. First, Borax is fine to increase pH when needed, but it does influence TA a little. The best way to increase pH with NO influence to TA is aeration. The more aeration you can create the faster the pH will rise.

About the TA itself..... while 120-140 may be a bit elevated, it's not crazy high and not something you have to attack too aggressively right now as long as you control the pH. PH is always more important because it has the most significant influence on your overall chemistry.

So next time you decide to try and lower TA, use the acid to lower the pH to about 7.0, then simply create aeration until the pH gets up to about 8.0 - then repeat. But if the pH is remaining stable in the 7.6-7.8 range, there is no need to beat yourself up with TA. Just leave it alone.

Don't forget to sign up for our PoolMath APP which is a great tool. Also update your signature with all of your pool and equipment details. It will help later.
Appreciate the response. A couple reasons why I went down this path after ignoring it for half of last season:

1. While my PH levels don't swing wildly, they're usually around 8 (or higher) every weekend so every weekend I'm adjusting them back down before swimming. I thought this could potentially stabilize them so I'm not constantly adding Muriatic Acid, even if it's only a relatively small amount every time.
2. The pool inspector when I purchased the home pointed out that the pool has a decent amount of calcium scaling on the walls and if I wanted to get the dark color back, I would have to have the pool acid washed. I'm not in a hurry to do this yet but wanted to get it under control so it didn't necessarily get worse and as I understand it, high TA contributes to this.
3. Scaling on my SWG builds up fairly quickly, though being new to a SW pool, it could be a 'normal' amount, I'm not sure.
4. Lastly I just bought a solar blanket cover to cover it during the week so I have to use less gas to heat it at the start of the weekend. I understand that it shouldn't be on constantly but I did leave it on for two weeks due to being out of town last weekend and when I removed it, the pool was green and PH low. It wasn't hard to bring it back to it's former crystal clear self but it sounded like the borates could help mitigate that from reading this thread: So you want to add borates to your pool--Why and How

I'll probably keep adding the borax and acid but it sounds like ultimately aeration is the way to go. I just have to figure out how to accomplish this with a return that isn't threaded and that I can't seem to adjust.
 
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rweiler994

Well-known member
Mar 27, 2021
87
Holts Summit, Missouri
Pool Size
10500
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair iChlor 30
I used to have an Intex pool and I also deal with relatively high TA, my water supply is around 300ish TA. While it may be a bit of a hassle, when you are not there if you have a small air compressor, get a cheap air hose and put pin holes in it and drop it in the water with the compressor running. I didn't end up using this idea as I was able to buy an inlet from Intex with an aerator, but I did look at Lowe's and I figured I could do this for about $20ish. Of course you would have to buy the ends, but a hose like this. If you don't have a compressor, this is similar to the one I have, it is oil free and not super expensive if you don't need the extra aeration all the time.
 

mgtfp

Bronze Supporter
Mar 5, 2020
931
Melbourne, Australia
Pool Size
66000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Astral VX 7T
Specifically my CYA has dropped to 50 from last seasons 80. I assumed this would only affect my chlorine levels so I haven't gotten around to bringing that back up yet but if that could be affecting it please let me know

There actually is one other reason apart from chlorine protection why higher CYA levels make sense with SWGs:

By adding CYA you replace some of the Carbonate Alkalinity (CA) with CYA-Alkalinity, keeping Total Alkalinity (TA) constant in the process.

Let's say you start with TA 90 and CYA 0. Pretty much all of the TA will be CA.

Now you add 80ppm of CYA; TA remains at 90ppm, but CYA-Alkalinity will now be about 25ppm (roughly 80/3), therefore CA will be reduced to about 65ppm. Only the CA-part of TA contributes to CO2-outgassing (responsible for pH-drift) and the CSI (responsible for scaling when too high, particularly within the SWG-cell). But CYA-Alkalinity is pretty much as good a buffer as CA, so you improved pH-drift and scaling without compromising on buffering.

Starting:
PH: 7.4
TA: 140

After Muriatic Acid:
PH: 6.8
TA: 125

After Borax:
PH: 7.4
TA: 140

I feel like I'm back to square one.

Your numbers make sense. With the MA addition that you added proactively to compensate the pH-rise by the Borax, TA remained more or less constant compared to the starting point (where pH was the same as after adding MA and Borax).

You feel like you are back at square one (which is true regarding pH and TA, but you have some Borates in the water now as well), but you are not done done yet. Just add more MA to bring pH down again (I wouldn't go below 7) which will also reduce TA again. Then you aerate to bring pH where you want it, keeping TA constant.

I used Chem Geek's PoolEquations spreadsheet to run a sanity check on your numbers (I calculated the amounts of MA/Borax to match your pH-values, assuming CYA 50):

Start:
pH: 7.4
TA: 140
BOR: 0

Adding MA:
pH: 6.8
TA: 115
BOR: 0

Adding Borax:
pH: 7.4
TA: 141
BOR: 12

Adding MA (just used pH 6.8 here again for simplicity, but I would recommend to stay above 7):
pH: 6.8
TA: 115
BOR: 12

Aeration:
pH: 7.4
TA: 115
BOR: 12

Considering tolerances, what you measured makes perfect sense. To the end result (regarding pH and TA) you could have gone directly with MA and Aeration only. But you have some Borates in your water now, which I consider a good thing with a SWG, but at about 10ppm they won't show much effect yet.

Just repeat the MA/Aeration cycle until your TA is where you want it. If you have issues with scaling, then this could make sense.

If you then still have problems with pH-drift and scaling in the SWG-cell, you could add more Borates (50ppm is recommended). Going the Boric Acid path would be easier (more pH-neutral), but you seem to know now how to add Borax in a pH-neutral way using MA...