PH and Dehumidifier? Weird Results!

Poseidon03 · Aug 6, 2023

Ok, hear me out. I'm an engineer so I have a decent grasp on science, but don't really understand this correlation I found.

First off, I have a 240 gallon tank in a larger room. I've had a PH swing of around 7.95-8.1 daily, and that was with kalk dosing at night. I turned my dehumidifier off and my PH changed to 7.88-8.0. I thought it was really weird because the dehumidifier only draws water out of the air, and my kalk is on a dosing pump, so it only doses so much. Extra evaporation wouldn't cause the increase. I thought it was just a fluke, but I kept the dehumidifier off for a month.

Just last night, I turned it back on and overnight the PH rose right back up. Maybe it is due to extra air movement in the room and equalizing the CO2 in the house? The tank has acrylic lids and a canopy, so I wouldn't think it would impact it like this. Also I would think a small dehumidifier wouldn't do this that well. Anyone else ever see something like this?

I'm going to see if the PH continues to be elevated this week or not. Maybe it was a fluke reading. It is weird how the PH dropped when it was turned off, though.

The_Paradox · Aug 6, 2023

We’re ATO volume numbers the same? Possible carbonic acid addition from standing water in ATO reservoir?

Poseidon03 · Aug 6, 2023

The_Paradox said:
We’re ATO volume numbers the same? Possible carbonic acid addition from standing water in ATO reservoir?

My ATO barely runs. I have a 5gal closed reservoir that I fill 1 time every 2 & 1/2 weeks or so. My kalk mix handles most of my top off (not much due to closed top, but I have an open back stand with a large sump).

Lps_lover12 · Aug 6, 2023

Following this, I have a 100 gallon in my bedroom. Not a very big room and there is just me and a small dog in there at night which causes my ph to drop below 7.6 each night. I run a dehumidifier during summer when the ac is on

Randy Holmes-Farley · Aug 6, 2023

I vote coincidence as most likely, the humidity of the air over the water won’t impact pH.

There are other possibilities…

1. Electrical interference with pH measuring device.

2. Altered air or water temp due to the dehumidifier.

3. Is the pH meter near the top of addition point? Adding pure fresh water can boost pH a bit, and it is has anything in it by accident (say, silicate), it may raise pH even more.

Poseidon03 · Aug 6, 2023

Randy Holmes-Farley said:
I vote coincidence as most likely, the humidity of the air over the water won’t impact pH.

There are other possibilities…

1. Electrical interference with pH measuring device.

2. Altered air or water temp due to the dehumidifier.

3. Is the pH meter near the top of addition point? Adding pure fresh water can boost pH a bit, and it is has anything in it by accident (say, silicate), it may raise pH even more.

1) The dehumidifier is 40ft away from the tank, so if there's electrical interference, there would be a bigger problem.

2) I would see an increase in temperature, which is right next to the pH probe if this was the case. They are both in a large room and have good air exchange through the kitchen and front room. It is a warmer room of the house, but no temp swing in the tank.

3) The pH meter is in the initial chamber of the return from the tank, where the skimmer is. The RODI water is added downstream, where the return pump is (dual return, 1 into skimmer and 1 into refugium; they are on either end of the sump and meet in the middle where the return pump is). The refugium is on a reverse light cycle. Kalk is also added where the return pump is. I wanted the least effect on my probes and wanted as accurate readings as I could get.