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Thread: Why does aeration cause an increase in ph?

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    Join Date
    Oct 2009
    Saint Cloud, FL

    Why does aeration cause an increase in ph?

    Hello, everyone! I'm new to this forum and I'm amazed at all the information available here. I've had lots of questions answered by perusing the different topics, but I've not seen a reason as to why aeration causes ph to increase. I just recently converted to a SCG pool, and the water is great, except for a steady increase in ph that I knock down with muratic acid. The aeration I have is from the return jets, and I believe it is caused by some air-sucking joints near the pump. The reason I think this is the source is that when the pump is turned off, water drips out fairly heavily from some of the pipe connections between the Jandy valves and the pump intake. This is from the water draining down from the solar panels up on the roof. Also, my solar panels leak in a few spots. I assume this could also be a source of air inside the system. Any help you can give me will be greatly appreciated! Thanks!
    16,000 gal IG plaster pool
    45 GPM cartridge filter & 1 HP pump

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Why does aeration cause an increase in ph?

    If you take a wander over to chemistry 201 there a a few threads about pH and areation. I'm sure chem geek will be along and give you the short version but you can use the Google search function at the bottom of the page if you'd like to read it on your own.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

  3. Back To Top    #3

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Why does aeration cause an increase in ph?

    Anything that increases the surface area of the air-water interface will increase the rate of carbon dioxide leaving the pool water. Aeration, as with air bubbles in water, is one way. Splashing or spillovers or fountains are another. Pools are intentionally over-carbonated both to provide a pH buffer and to saturate the water with the carbonate portion of calcium carbonate to protect plaster surfaces from dissolving. In other words, there is a lot more dissolved carbon dioxide in the water than would naturally occur in equilibrium with the air (though obviously not as much as a carbonated beverage!).

    As for why the pH rises, the easiest way to explain it is that some of the carbon dioxide in water is carbonic acid -- that is, carbon dioxide plus water makes carbonic acid -- so removing carbon dioxide is like removing carbonic acid. Removing an acid from the water makes the pH rise. One of the posts on this subject with the chemical equations is here.

    Your saltwater chlorine generator, however, may also increase pH through another mechanism in addition to the increased aeration from the hydrogen gas bubbles. The chlorine gas itself may not fully dissolve in the water. If any escapes without dissolving, then the net result is a rise in pH since the net neutrality in pH depends on the chlorine gas dissolving in the water to form hypochlorous acid, which is an acidic process, and on the chlorine getting consumed either by breakdown in sunlight or oxidizing bather waste or other organics, which is also an acidic process. More chemical details about this are in this post.

    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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