pH of RO/DI H20

[MPL]

I have a Kent Marine RO/DI (reverse osmosis/deionization filter) and was wondering if it is normal for the pH of the filtered water to be around 7.4 (Oakton pH meter). I've read the RO units should produce water around 5.7 because of rapid CO2 and O2 absorption, but my unit has the deionizer and I'm not sure if that changes anything. The filters are brand new with only maybe 200 or 300 gallons through them.

The water coming out should be pure as I have used it to keep and breed ultrasensitive Acropora sp. and other delicate corals.

 

[Guest]

That's right MPL it should be lower. If one is run without having good carbon filters before it, it will die and the ppm and the pH will go up. The chlorine destroys the membranes.

Also just being run so that too much water is forced through them will ruin them.

Is it new, used, set up as far as you know - right?

 

[MPL]

It's hooked directly up to my sink faucet, and I seriously doubt that creates enough pressure to ruin the membranes. There have been a few times that the output hose was blocked, but that didn't change anything.

I haven't checked this in awhile, but last time I had to use pH down to drop the pH it took very little of it to reach my target.

There is very little waste water produced, which is kind of surprising for me as the water around here seems quite hard. Just a little bit splashed around the sink will leave calcium deposits when it dries.

I wish I had an EC meter. bleh

I got it from a family member, who also used it to keep very sensitive corals and other marine organisms. I got a brand new set of filters before I changed it from aquarium use to hydroponics use. As far as I know, it always has been and currently is set up correctly.

I'm really trying to avoid using pH down, but I've got nutes at full strength in my E&F setup and the pH is still around 6.0 - 6.2. If it matters, I am using FloraNova Grow at 8mL/gallon in a 13 gallon reservoir (14 gallon Rubbermaid tub). I am having to add about 0.5 - 1.0 mL/gallon of pH down to get the pH down to 5.7.

That's right MPL it should be lower. If one is run without having good carbon filters before it, it will die and the ppm and the pH will go up. The chlorine destroys the membranes.

Also just being run so that too much water is forced through them will ruin them.

Is it new, used, set up as far as you know - right?

 

[Tactical Farmer]

Did alot of tests with my meters & could never get the water from my RO/DI to read anything - its just Blank - Guess its so pure that meter doesn't even recognize its in liquid ?

 

[MPL]

That would be crazy. lol I guess it is possible, if you think about how meters measure the pH. What kind of filter?

Did alot of tests with my meters & could never get the water from my RO/DI to read anything - its just Blank - Guess its so pure that meter doesn't even recognize its in liquid ?

 

[chiliwalt]

Did alot of tests with my meters & could never get the water from my RO/DI to read anything - its just Blank - Guess its so pure that meter doesn't even recognize its in liquid ?

Something is wrong w/ your test gear. It doesn't matter if your water is so filtered that the PPM's are 0 -which is darn near impossible- your ec or ppm test device should read 0. Dig? MPL that ph is about what I get, my tap water runs about 230 - 290 PPM (varies), PH 7.5 - 8.0, RO water: 9 - 39 PPM (depending on how new my filters r), with a ph very slightly lower than tap. The diff is tap is much more stable. RO water swings down very dramatically w/ one drop of phosphoric acid. The same volume of tap water requires a much larger amount of PH down in order to achieve the same results. Tap holds it's PH better in the res too -IMHO- naturally occurring minerals in tap provide buffering qualities.

Hope this helps, Chili

 

[Guest]

What he says is true; it could have a pH that high, but just a single or two individual drops of pH down should move it down a lot. If you add some nutes to it, it should drop it, too; since most fert mixes are acidic. As I recall seeing ppl say, GH nutes tend to buffer water to about 6.

If you can add nutrients to it, or a couple of drops of pH down to it, and the pH doesn't drop a lot, there's something wrong.

If the membrane's in good shape you should be having very few ppm out of it and a pH down around six, and not much higher with new pre filters. That's effectively no calcium or magnesium left to buffer the pH up higher; and the slightest acidic substance should make it fall way down.

Some kind of ppm/ec meter is going to be a pleasant investment in the long haul.

 

[chiliwalt]

double post sorry

 

[chiliwalt]

H2o in it's pure form has a neutral ph of 7.0. Yeah the salts in nutes both organic and inorganic are very acidic esp. nitrogen. Once you add nutes to RO water it usually has to be ph'd up, w/ a base of some sort. As it goes down past 5.8, tap water on the other hand usually ends up right at 5.9 or 6.0 after nutes are added.

Hope this helps, Chili

 

[MPL]

Awesome ok so RO water doesn't always drop the pH way down. Good to know, because the water coming out of my unit doesn't seem to leave any deposits when it dries. Also, I have noticed that it doesn't take a lot of GH pH down to swing it. Just 1/4 tsp will take a gallon from 7.6 to like 7.0 if not lower.

I have noticed that my res pH is skyrocketing up every day. It went from 6.2 to 6.8 in less than 24 hours yesterday. It went from 5.7 last night to 6.2 this afternoon (about 18 hours elapsed). Evaporation would be causing the pH to drop, not rise, yes? I have noticed about one gallon evaporating every 24 hours or so out of my 13 gallon res. I know the plants are not using nutes to the point that it would move the pH that fast because they are tiny little clones, barely showing roots outside of the rockwool.

Could this be because I soaked and rinsed my hydroton in plain tapwater with a pH of around 7.5?

MPL that ph is about what I get, my tap water runs about 230 - 290 PPM (varies), PH 7.5 - 8.0, RO water: 9 - 39 PPM (depending on how new my filters r), with a ph very slightly lower than tap. The diff is tap is much more stable. RO water swings down very dramatically w/ one drop of phosphoric acid. The same volume of tap water requires a much larger amount of PH down in order to achieve the same results. Tap holds it's PH better in the res too -IMHO- naturally occurring minerals in tap provide buffering qualities.

Hope this helps, Chili

 

[MPL]

My starting pH is 7.4-7.6 (seems to vary a bit, even if the only thing different is the container it is measured in). 5mL/gallon of GH FNG will drop it to about 6.5ish. 8ml/gallon is around 6.1.

What he says is true; it could have a pH that high, but just a single or two individual drops of pH down should move it down a lot. If you add some nutes to it, it should drop it, too; since most fert mixes are acidic. As I recall seeing ppl say, GH nutes tend to buffer water to about 6.

 

[00420]

mpl...... im a reefer too 80 gallon display 28 fuge 20L sump

my tap is 7.5 350ppm
after r/o it is 7.2 002ppm
r/o from a galicier Vending Machine is 7.1 001ppm

 

[MPL]

Nice setup! What are you keeping in it?
That information was really useful, thanks!

mpl...... im a reefer too 80 gallon display 28 fuge 20L sump

my tap is 7.5 350ppm
after r/o it is 7.2 002ppm
r/o from a galicier Vending Machine is 7.1 001ppm

 

[00420]

Nice setup! What are you keeping in it?
That information was really useful, thanks!

right now i just have a frogspon and a seabay anim
100 pound's of LR with killer purple algee
1 purple tang
2 nemo's
3 fire shrimp
1 sally lite foot crab
2 purple/pink firefish (i belive thats what there called)
100 or so hermits (mixed type's)
100 or so snails ( mixed type's)

i have not got into to many corals yet tank has been up just over 6 months do to moving befor i moved it was a fish only

 

[MPL]

I bet you laugh when people talk about how expensive a grow op is.

I hope you don't have any predatory snails or hermits. That crab could become a real threat to the reef as well. The froggie could become quite tasty to it. hehe Then again, it may just eat detritus all its life.

Sounds like a real nice setup. In a couple of years, with more corals and whatnot, you'll have a little slice of the Pacific.

right now i just have a frogspon and a seabay anim
100 pound's of LR with killer purple algee
1 purple tang
2 nemo's
3 fire shrimp
1 sally lite foot crab
2 purple/pink firefish (i belive thats what there called)
100 or so hermits (mixed type's)
100 or so snails ( mixed type's)

i have not got into to many corals yet tank has been up just over 6 months do to moving befor i moved it was a fish only

 

[00420]

I bet you laugh when people talk about how expensive a grow op is.

I hope you don't have any predatory snails or hermits. That crab could become a real threat to the reef as well. The froggie could become quite tasty to it. hehe Then again, it may just eat detritus all its life.

Sounds like a real nice setup. In a couple of years, with more corals and whatnot, you'll have a little slice of the Pacific.

man a reef doubles a grow op easy lol

the snails & hermits are reef safe i got them from GARF the froggie and crab have been together for about 4 months now and it has not even thought about it so im good there hehe..... i belive theres plenty for him to eat in there if he dose become danger i can allways stick his ass in the sump i think the fuge keeps the tank pertty well stocked on food for him
my skimmer is made for a 250-300 g tank