ph in r/o water still close to city tap water - need aeration?

[Jandiscus]

My local city water comes in at a ph of 9. After going through the r/o system it is still at 8.8 after 12-24 hours and 8.2 after a week. This is all in the holding tanks with no biological activity. I find that strange since I thought that r/o water with a dKH of 1 would settle at a much lower ph right out of the unit. Apparently not?! I did not add an air stone to it yet and don't think that I ever did in the past on r/o water. I did that on tap water to help drive out the chloramine but not on r/o. Any guidance on this? Obviously, I was banking on the r/o water in combination with aged city water to give me a suitable ph somewhere below 8 so that I don't have to mess with it. I didn't have that issue in my previous location as my ph was lower to begin with.

Thank you for any insights you might have.

[Iminit]

I’m not an ro user. But from all I’ve read on these systems when the water comes out it should be at 7.0. May be more waste water but it should end up at 7.0. If not why use it? Could there be a problem with the system? A tear in the membrane?

[Second Hand Pat]

I would also suggest adding a airstone to the RO water. See if that affects ph overtime.
Pat

[brewmaster15]

My local city water comes in at a ph of 9. After going through the r/o system it is still at 8.8 after 12-24 hours and 8.2 after a week. This is all in the holding tanks with no biological activity. I find that strange since I thought that r/o water with a dKH of 1 would settle at a much lower ph right out of the unit. Apparently not?! I did not add an air stone to it yet and don't think that I ever did in the past on r/o water. I did that on tap water to help drive out the chloramine but not on r/o. Any guidance on this? Obviously, I was banking on the r/o water in combination with aged city water to give me a suitable ph somewhere below 8 so that I don't have to mess with it. I didn't have that issue in my previous location as my ph was lower to begin with.

Thank you for any insights you might have.

Jan,
I would check your R/O filter...be sure its working. Whats your TDS before and after the filter?

al

[Jandiscus]

I would also suggest adding a airstone to the RO water. See if that affects ph overtime.
Pat

Thank you Pat! I will do that to see if it makes any difference.

[Jandiscus]

Jan,
I would check your R/O filter...be sure its working. Whats your TDS before and after the filter?

al

Thank you Al, This is a brand new r/o unit. TDS is 750+ pre and <100 after. I will take more measurements as this still puzzles me. I might also bring the other unit I was previously using at my other place. I am just glad that I am addressing all these startup issues before adding fish. Unlike in the past, where I bought fish before I bought the tank :-) Well, not quite....but close.

[Jandiscus]

I’m not an ro user. But from all I’ve read on these systems when the water comes out it should be at 7.0. May be more waste water but it should end up at 7.0. If not why use it? Could there be a problem with the system? A tear in the membrane?

Agree!

[Jandiscus]

Thank you Al, This is a brand new r/o unit. TDS is 750+ pre and <100 after. I will take more measurements as this still puzzles me. I might also bring the other unit I was previously using at my other place. I am just glad that I am addressing all these startup issues before adding fish. Unlike in the past, where I bought fish before I bought the tank :-) Well, not quite....but close.

Looking at the city’s water measuring report, it states that tds on average is 294 and as high as 500 mg/L, although my $30 measuring probe says that it is higher. Ph is stated to be 9.57.

[brewmaster15]

Thank you Al, This is a brand new r/o unit. TDS is 750+ pre and <100 after. I will take more measurements as this still puzzles me. I might also bring the other unit I was previously using at my other place. I am just glad that I am addressing all these startup issues before adding fish. Unlike in the past, where I bought fish before I bought the tank :-) Well, not quite....but close.

Jan its hard to believe that with 100 TDS Your pH is that high.. if you havent calibrated it recently .. I would try that.


Municipalities often raise the pH with various chemicals to protect pipes.. its possible something they add is getting through. A solution is to add a DI resin.. that should remove it.

I doubt theres much buffering left in that water.. any acid will make it drop... might be worth trying see how stable the pH is