Aerating your water before taking a pH reading

I asked this on another forum and it didn’t seem that anyone was understanding me there so I figure I’ll try here.

I still have seedlings going so I’m still using distilled water but when I transition over to tapwater I have a question. I have to use well water as the grow is located remotely indoors. As it comes out of the tap, the water contains a high value of CO2 because it’s well water. Generally most well water measures low in pH due to how the water is filtered through the soil back into the ground. I believe the processes that occur in the ground the deeper it gets become anaerobic and oxygen doesn’t work in the process. So when the water comes out of the tap it’s around 5.9 or so. Once aerated, especially outside, the pH comes up higher than 7 due to the CO2 being removed.

The question I have this time is, does anyone else use well water and if so are. you aerating it to bring up the pH and remove the CO2 prior to taking your measurement?

My concern is that taking a measurement then adjusting WITHOUT aerating will likely cause an incorrect reading depending on what happens to the pH of the water and soil once the water hits the soil and “breathes”. Does this cause the pH in the soil to go up due to CO2 being released once it hits the soil or sits in it for a while?

I guess another question I have is does the excess CO2 in the water hinder growth due to there possibly being excess CO2 released in the soil around the roots when the roots actually need oxygen?

If anyone has checked this out would you recommend aerating with room air to stabilize and THEN adjust before watering or adding nutes?


@Hellraiser @dbrn32 @Myfriendis410 @imSICKkid @MattyBear @KeystoneCops
No idea, but I’m tagging anyone who will tag another to get answers.
A lot of people use well water without aeration, and they do just fine.


Yeah, don’t do that, aerate it first, then add nutes, then ph adjust.


@Titleist I use tap water but from where I live I test the pH and is aroun 7.3 so I just pH down to my soil recommend I look ppl they co2 the water and control the ph to the recommend

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I’d set out a couple test buckets now before you need to start mixing solution.

I don’t think your well water would be too far off of equilibrium, but it’s possible that it could lose or gain hydrogen when exposed to air.

Aeration is a little overrated. Do it if you can. Don’t sweat it if you can’t.

I’d test the water for TDS, then pH. Use the data from your test buckets to determine when the water will reach equilibrium.

Did I clear things up?


My well water runs pretty consistently at 7.5 so I have to use Ph down.


My well water will work without aeration just fine. I don’t typically use it though because it’s pretty hard without being treated.


I read somewhere that aeration lowers the PH temporarily due to the dissolved CO2. But it’s transient.


Actually the other way around :slight_smile: CO2 depresses pH, aeration gets rid of it and you’re usually left with about 8.3 when fully degassed depending on what else is in the water. I found this out through a reef tank I run. pH ideally is around 8.3 for what’s in my tank, topping off evap water alone with just tapwater or RO water slowly depresses pH unless you use algae in a sump or have good room circulation to remove the CO2. Left alone with the windows closed the pH in a circulating pool of water in the room the pH will drop due to CO2 in the room.

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