Lowering pH using R/O water

[twoluvcats]

Ok, this has been baffling for me. The R/O water's pH would test out different for me every time I did it....I was starting to think my pH test went bad. But I finally started to get consistent results...it must have been stabalizing or something (very new system). Here's what I have:

R/O Water:
pH: 7.2
KH: <40
GH: <5

Softened Tap Water:
pH: 7.6
KH: 120
GH: <5

2.5 Gallon Tank (has had softened water added):
pH: 7.6
KH: 180
GH: 150

2.5 gallon tank (no softened water added, office tank):
pH: 7.6
KH: 80
GH: 300+

I'm ballparking the KH and GH cause I could only get a dip-strip test. I've ordered a regent test from Big Al's so I should have that next week.

Sooooooooo...my water that's supposed to be ~6.5 pH isn't. Its 7.2. Am I going to be able to get my water to 7.0 without jumping thru a million hoops?...I bought a bottle of Seachem's 7.0 regulator/stablizer...i have not used it yet, or do i plan to until I get closer to 7.0.

These numbers are all over the place...but our water's pretty messed up...its contaminated before it hits the water plant, and then the water plant treating it is 30+ years old and built for 200 people while supporting ~1000. (they are building a new one next year)

What will potassium do? Occasionally, the city dumps it thru our system...turns the water pink if you don't have filtration. I make a point not to add that water (or drink it myself) for a couple days when it happens...but now that I have a filter I won't see the pink to know...i'm hoping that the softener and sediment filters will take it out.

aaaaaaah a chemistry challenge

[amanichen]

twoluvcats said:

<lots of stuff about her water>

So uh, refresh my memory...what water are you trying to mix with what water, and what is your target pH for the mixture?

What will potassium do? Occasionally, the city dumps it thru our system...turns the water pink if you don't have filtration. I make a point not to add that water (or drink it myself) for a couple days when it happens...but now that I have a filter I won't see the pink to know...i'm hoping that the softener and sediment filters will take it out.

Pink?

That's not just potassium. It's potassium permanganate, which is KMnO4. It's both a sterilizer, and a powerful oxidizer. Do you know why they're putting it in the water? For cleaning purposes maybe?

It's a relatively powerful oxidizer, and I wouldn't use water treated with it in your tank, and I certainly wouldn't drink the stuff.

Potassium itself isn't really deadly -- like sodium it's just another electrolyte that is necessary for plants and fish. Most freshwater fish can tolerate about 20ppm without any problems. Some aquarium fertilizers end up producing 20ppm of potassium chloride.

[twoluvcats]

So uh, refresh my memory...what water are you trying to mix with what water, and what is your target pH for the mixture?

I'm trying to get my pH down from 7.6-8.0 to something near to 7.0 as I can. I've got R/O water, and softened water to mix.

potassium permanganate Do you know why they're putting it in the water? For cleaning purposes maybe?

I'm sure its for cleaning...most likley undisclosed failures at the water plant...so they use the potassium permagnate to clean out the system. They also run it after we have water main breaks...to combat the turbidity that flushes out of the dead-end pipes. It not a weekly occurence...more like every six months or so...but it is something I have had to be aware of. But now I wonder if I'll be able to see it with the new water system.

[amanichen]

twoluvcats said:

I'm trying to get my pH down from 7.6-8.0 to something near to 7.0 as I can. I've got R/O water, and softened water to mix.

Two weeks ago your R/O water tested at a pH of 6.2, and now it's up at 7.2. If that's the case, then I'd just use all R/O water, and then put a buffer (either a prepared formula or lime or baking soda) into it to provide a KH boost.

If the R/O water was 6.2 you'd be mixing it with the softened tap water, but since it's 7.2, don't even bother mixing it...the lowest pH a mixture of two waters will go is the pH of the lowest source. Basically, you won't get to 7 unless one of them is at or below 7 =)

[twoluvcats]

and then put a buffer (either a prepared formula or lime or baking soda) into it to provide a KH boost.

does this stuff work as a buffer?

[amanichen]

twoluvcats said:

does this stuff work as a buffer?

Yup =)

As a general rule, stuff from Seachem works as advertised.

Of course any buffer works best if the water is already at the target pH, but it's one of the better buffers that you can get (i.e. it's not made by aquarium pharmaceuticals or wardley)

[twoluvcats]

Finally, I bought the right product the 1st time!! LOL

[amanichen]

twoluvcats said:

Finally, I bought the right product the 1st time!! LOL

Hehe =)

[twoluvcats]

Two weeks ago your R/O water tested at a pH of 6.2, and now it's up at 7.2.

Just a clarification...I was TOLD the pH would be ~6.2 by the guy that installed the system, but so far my R/O water has never tested that low. The wacky tests I was getting were between 7.0 and 8.2.

[amanichen]

twoluvcats said:

Just a clarification...I was TOLD the pH would be ~6.2 by the guy that installed the system, but so far my R/O water has never tested that low. The wacky tests I was getting were between 7.0 and 8.2.

Keep track of what it tests, when you test it. Keep a log to keep track of changes.