pH of RO/DI water

[Aquattro]

RO water is generally around 6ish. Pure water is a theoretical substance

Slight amounts of CO2 can lower it. From what I just googled, it can actually be anywhere from 4 to 12...

Not that it really matters what pH it is, since we're dumping a whole lot of salt into it

[fencer]

But my make up water doesn't have salt in it. Might be worth putting some calcium reactor media in the make up tank

[Aquattro]

No, you're adding water to make up for the evaporation. The minerals of the evap are still there and will combine with the fresh, leaving it in a state as before the evap. You don't need to do anything.
The reason it's 6 is that it has no carbonates in it (alk ) and any slight uptake of CO2 can affect the pH a lot. Once it's added to the bigger solution containing carbonates, the buffering capacity will return and you're good to go.

[mike31154]

Originally Posted by fencer

But my make up water doesn't have salt in it. Might be worth putting some calcium reactor media in the make up tank

Or aerate it to introduce oxygen, deplete CO2. This should raise it closer to the level preferable for our tanks.

[Aquattro]

Originally Posted by mike31154

Or aerate it to introduce oxygen, deplete CO2. This should raise it closer to the level preferable for our tanks.

Or not worry about it instead

[mike31154]

Originally Posted by Aquattro

Or not worry about it instead

Actually yes, that's what I end up doing - nothing & not worrying. Only time I measure pH these days is when introducing or acclimating new livestock & occasionally before/after a water change. Gives me a better idea of how long I may need to acclimate or if can safely add some alk, since that seems to be forever low in my system.

[ScubaSteve]

When my water comes out of my lab RO/DI the pH is usually pretty close to 7 (6.8-6.9) but within 5 to 10 mins the pH drops to 6 simply due to CO2 dissolving into the water. There's no need to worry about it though. If your wanting to keeptue top water close in pH, add a tiny bit of Kalk to buffer it.

[cwatkins]

Guys, what's Rule #1? Don't worry about pH!

Ok ok, I do see the point to this thread though. I should check my water and see what pH we get in Metro Vancouver. Interesting....

[mike31154]

Yeah, I pretty much posted what I googled as well, as far as what the definition of neutral pH is. Interesting reading though on some facts re pH. Worth noting that the pH scale is logarithmic by a factor of 10, hence the caution when fiddling with pH numbers in our systems.

There's a nifty pH scale on this link showing the values of some common items.

http://hyperphysics.phy-astr.gsu.edu...emical/ph.html