PH of our Water Supply...

[rbredding]

I was over at Jonboyb's this weekend and he and I were talking about tank stuff..

he brought up that our municipal tap water has a pretty low ph.. I told him that I'd never tested it for anything but TDS..


then I tested it..


the PH at my house was 7.6 !!

NO WONDER, I couldn't keep my PH up... I will buffer it from now on


have y'all tested your municipal supply (or well, if you're so plumbed)

 

[jeffh]

pH of the tap water shouldn't have anything to do with pH of mixed saltwater. All the ions are removed by the RO/DI and the ions put in by the saltwater will determine it's pH.

 

[lilrobb]

Yup,

what he said.

Plus pH probes at RO/DI SUCK, they will read all over the place

 

[darcurr]

JeffH;633327 wrote: pH of the tap water shouldn't have anything to do with pH of mixed saltwater. All the ions are removed by the RO/DI and the ions put in by the saltwater will determine it's pH.

+1

Especially if you use ro/di water.

 

[rbredding]

huh?

so what would the PH be of the filtered water on the PH scale (0-14)
neutral is 7, 0 is basic, 14 is acidic..

?

it's GOT to be somewhere between 0 and 14


(measured the ph with my probe hooked to the Apex)

 

[lilrobb]

basically an electronic probe cannot pick up 7, there are no ions in there to register so unless you have a multi-thousand dollar meter they will read funky stuff every time you get a reading...

 

[livingroomocean]

I stick a pump in my ATO/makeup container (150g) and feed a Air line to the pump - to get over the issue of very low PH from my RODI -

 

[insane_reef_keeper]

Our water here is right at 8.0, so no problems here so far. Although we do have well water so that's probably why it is where it is.

 

[rbredding]

so y'all are telling me that every tank, everywhere in the world, that puts topoff water (filtered with rodi) in a tank is the SAME?? (assuming the rodi is properly filtering the water)..


and are you telling me that topoff water will not change your PH... (lowering it, either by having a lower ph itself, or by lowering the SG of the system)


?

Edit:

insane_reef_keeper;633370 wrote: Our water here is right at 8.0, so no problems here so far. Although we do have well water so that's probably why it is where it is.

what is your water after RODI?

 

[ichthyoid]

Rbredding;633338 wrote: huh?

so what would the PH be of the filtered water on the PH scale (0-14)
neutral is 7, 0 is basic, 14 is acidic..

?

it's GOT to be somewhere between 0 and 14


(measured the ph with my probe hooked to the Apex)

Actually it's the other way around, 0 is acidic and 14 is basic.

Anyway-

When measuring pH, the number represents the 'anti-log (or negative logarithm) of the molar hydrogen ion (H+) concentration'. Say what?....

OK, 0.1 molar HCl (hydrochloric acid) would be pH of 1.0, very acidic; and
0.0000001 (1x10^-7) molar HCl would be a pH of 7.0. For the pH to be any higher, there must be some base dissolved in the solution.

A pH of 7.0 has as many H+ ions, as OH- ions. That's why we say it is neutral.

It gets better. You can also measure the logarithm of -OH ions, which will represent the same thing. Because of some minor technical nuances in chemistry, it was agreed long ago to use the H+ measurement.

Your water at pH 7.8 is actually basic, just not very strongly so.

Once you go through a DI resin filter, essentially all of the ions are removed. There are actually a few left, but not enough to measure, as Robb mentioned. The probe is comparing the ions to a standard reference it has built in. It's like having a 0 in the denominator (bottom part) of a fraction, the result is 'undefined'.

Topoff water that has gone through a good DI resin stage cannot change the pH, as there are no ions present to do so. After the DI stage the pH will be 7.0 (assuming both the probe/meter and the DI resin are good).

Here is a link for more info-

 

[ichthyoid]

Also, CO2 will be absorbed by DI treated water and become acidic. To prevent this either keep in a vacuum or purge the storage container with an inert gas, such as nitrogen.

 

[rbredding]

so testing the ph of your topoff water will give you a better view of how your DI stage is working (than TDS will)...

 

[ichthyoid]

No, as mentioned, the pH reading of DI water can be unpredictable. TDS measures conductivity. It is more reliable, IMO. It's also what big name filter companies use on research grade DI water systems, FWIW.

 

[rbredding]

hahaha!!

ok...

so as long as my RODI water reads 000 TDS then Im cool..

However : (for the purpose of complicating the issue)

doesn't it effectively lower the PH of my system when I topoff with water that isn't buffered to a higher ph than neutral

ichthyoid;633388 wrote: Actually it's the other way around, 0 is acidic and 14 is basic.

that's actually what I meant to type... (dunno why my fingers messed it up)

 

[ichthyoid]

Rbredding;633409 wrote: hahaha!!

ok...

so as long as my RODI water reads 000 TDS then Im cool..

However : (for the purpose of complicating the issue)

doesn't it effectively lower the PH of my system when I topoff with water that isn't buffered to a higher ph than neutral





that's actually what I meant to type... (dunno why my fingers messed it up)

No; with no disolved ions, the DI topoff water has no effect on your tanks pH.

I figured you got them crossed up, just didn't want any confucion. A lot of folks watch, without responding.

 

[rbredding]

ichthyoid;633427 wrote: No; with no disolved ions, the DI topoff water has no effect on your tanks pH.

I figured you got them crossed up, just didn't want any confucion. A lot of folks watch, without responding.

why not?
I get that there are not additional ions added, but you're diluting the ions over a larger volume of water..

 

[ichthyoid]

Rbredding;633432 wrote: why not?
I get that there are not additional ions added, but you're diluting the ions over a larger volume of water..

No you are not. You are just replacing evaporated water.

Think about this-
If your ATO is any good at all about keeping up with evaporation, the ion concentration will stay essentially the same. Ions do not evaporate, only water does. It is replaced at the same rate it evaporates. The amount of ions, and the amount of water are constant.

(of course in practice, some CO2 is absorbed by the water and THAT will lower the pH a bit)