How do those with waterfalls deal with high PH

durtynacho

Active member
Aug 4, 2015
32
Ellis County, TX
Aeration obviously raises PH. For those with waterfalls or fountains or other nice add-ons that contribute to natural aeration, how do you deal with your PH? Assuming you have your alkalinity in check, does your PH remain at an appropriate level regardless of aeration? Or, does it rise and require being dealt with on a regular basis? Seems like it would be a constant see-saw effect with having rise, having to lower it, so on and so forth.

I ask because I made a homemade aerator to get my alkalinity down, and now that I've done that, I'd like to run it regularly because I like the effect. But I don't want to inadvertently cause my PH to spike as a result, and that seems inevitable. It also seems inevitable to occur for anyone with any sort of waterfall type component.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,214
Tucson, AZ
I have both a natural stone waterfall (driven by a 3-HP pool pump so it is very powerful) and a spillway from my raised spa to the pool. This creates a lot of aeration. The main way I deal with this aeration is first by running my water features for the absolute least amount of time possible (they are all automated with programmed schedules). Next, I keep my TA as low as possible (typically 60ppm or less). And finally, I use 50ppm borates in my pool water to act as an additional buffer against pH rise. By doing all this, I can keep my muriatic acid additions to about 16oz of acid every 10 days or so.
 

durtynacho

Active member
Aug 4, 2015
32
Ellis County, TX
Ahh, so it's all in the borates. Thanks for the replies. I knew acid was used to lower PH, but it will also lower TA which will then need to be raised if it gets too low which is why I was concerned about a see-saw effect.

I will look into borates. Thanks!
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,214
Tucson, AZ
Ahh, so it's all in the borates. Thanks for the replies. I knew acid was used to lower PH, but it will also lower TA which will then need to be raised if it gets too low which is why I was concerned about a see-saw effect.

I will look into borates. Thanks!
Actually, it's not all in the borates. In fact, borates will only help a little and, for some, there was/is no improvement at all when borates were added.

pH rise from aeration is not a independent, constant process; it is integrally related to your TA level. You TA and pH levels determine the amount of dissolved CO2 in your pool water (more dissolved CO2 the lower the pH and higher the TA). When you aerate your pool water, you liberate CO2 from the water (a process called outgassing) and, because you have bicarbonate ion (HCO3-) dissolved in your water, an equilibrium reaction occurs whereby the bicarbonate ion consumes a proton (H+) in order to restore the amount of CO2 lost from aeration. When this bicrabonate/CO2 shift happens, your pH rises. As you add acid to lower the pH, the TA gets lowered as well. As the TA decreases, so to does the amount of dissolved CO2 allowed by the equilibrium chemistry. Because of this lowering of the TA, the rate at which pH rises from aeration gets slower and slower. Eventually, if the TA is low enough, the amount of pH rise will stop and you find yourself (sometimes, not always) at a balance point.

This is why when people experience pH rise form aeration, we first tell them to lower their TA and try to find a TA level that minimizes the frequency of acid additions. Sometimes their acid demand problem can be solved simply by lower TA, sometimes it can't and then borates are recommended. So, in your case, rather than running off and buying expensive chemicals, why don't you first run your aerator/fountain for a while and see what happens. You may not, in fact, experience much pH rise at all. Even if you do, your first order of business is to lower your TA to try to correct the problem, not add borates.
 
  • Like
Reactions: Soupy

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,476
Franklin, NC
Because of this lowering of the TA, the rate at which pH rises from aeration gets slower and slower. Eventually, if the TA is low enough, the amount of pH rise will stop and you find yourself (sometimes, not always) at a balance point.
This is why I keep my TA down in the 50ish range. It has slowed my acid additions greatly.

But, this is also why we say that mixing TFP and pool store advice won't work. For amusement I sometimes take my water to pool stores to see what they say. Invariably I am told my TA is dangerously low and I need to buy their fancy magic powder to fix it immediately. I respectfully decline. I have even tried teaching some why I keep it that low but I'm generally told I don't know what I'm talking about and I should buy their stuff.
 

Jonesbackr

Gold Supporter
Jul 22, 2018
26
Lufkin, TX
Posting here in the hopes that someone still follows this thread. One thing I’m confused on is I use the same treatement to lower my pH and my TA: muriatic acid. Is there something else I should be doing to lower TA or should I just run it down? My pH is good right now (7.7)but my TA is around 90.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
12,432
Evans, Georgia
One thing I’m confused on is I use the same treatement to lower my pH and my TA: muriatic acid. Is there something else I should be doing to lower TA or should I just run it down? My pH is good right now (7.7)but my TA is around 90.
No, the only way to lower TA is to use the MA. Obviously this also takes your pH down, but a bit of aeration (or kids splashing about wildly) will cause the pH to rise again. I've used fountains and sump pumps at times to raise my pH.
IMG_0481 copy.JPG