R.O. water ph is way off.

Discussion in 'Growing Marijuana Indoors' started by toilofday, Jan 22, 2010.

  1. I bought 2 different kinds of RO water, foodclub distilled by reverse osmosis, and walmart green cap. Both tested at a ph about 5.2. This confused me greatly. I though RO water was supposed to be 7.0. I even bought new indicator solution General hydroponics brand to test it so I know I didn't screw up.

    Any ideas on a place to buy good water?
  2. Just because it is reverse osmosis doesn't mean it is a perfect 7.0 solution. And what do you mean by good water? You can't buy any better water than RO water for growing pot.

    Buy some pH - up, problem solved.
  3. #3 zpyro, Jan 22, 2010
    Last edited by a moderator: Jan 22, 2010
    I think the issue is that there really isn't anything in the water to measure it, because it's so pure. I bet if you put any pH up in there, the pH will jump up to 10 or something. I put some tap water in the RO to act as a slight buffer if I'm worried about the pH of plain water. I know that with distilled water, carbon dioxide in the air will dissolve into the water and create carbonic acid, lowering the pH
  4. what is R.O water?

  5. It's water thats been filterd using Reverse osmosis.

    Basicly it lowers the amount of particles in your water, which is commonly referred to as "parts per million'. Plants can only feed from water with a limit of PPM levels, so if you can lower your waters PPM through R.O, it means you can add more Niutrients/additives.
    It also removes alot of crap from normal tap water that your plant really doesnt need, like chlorine and fluride.
  6. Not necessarily true. You use RO so your beginning PPM is as close to 0 as possible. That way when you add nutes you just read what your meter says and that's pretty much your true PPM. If you use tap water it can have a couple hundred PPM depending on where you live, if you don't account for that then your measurements will be off. RO does remove any chlorine, metals etc that are normally dissolved in tap water. When all you're adding is pure water and your nutes, you don't have to worry about what might be in the solution. As I said though, I use a little tap water to balance out the pH. Tap water is pretty close to 7, with the minerals and such that are in it the pH is more stable. When I put nutes in plain water sometimes the pH is a bit low, some tap water brings it up to where it needs to be
  7. #7 toilofday, Jan 22, 2010
    Last edited by a moderator: Jan 22, 2010
    Unfortunately no. It takes a full drop of General Hydroponics PH up per 20 oz bottle to get the water in range. Right now i'm using more than that to counter the lockout i've accumulated.

    that's a lot if I compare it to using ph down when I was getting 7.0 ph green cap walmart water.

    something is wrong with this water. Apparently when they remineralize RO water it has to fall within a ph range of 6.8-8.1 So I have defective water.

    Does anybody use culligan or Primo water? Do they have more stable water?
  8. I'm using primo water from kmart 5 gallon jug and I'm getting 6.9 ph

    Sent from my SCH-I605 using Grasscity Forum mobile app
    I haven't done a cal. on my meter in a month but after I cal. I'll let you know

    Sent from my SCH-I605 using Grasscity Forum mobile app
  9. #9 howando, Nov 16, 2014
    Last edited by a moderator: Nov 16, 2014
    The reason that pure water is pH < 7 is because of the dissolved carbon dioxide gas from the atmosphere.  It forms an equilibirum by reacting with the water and forming carbonic acid.  Actually at atmospheric pressures, pure water would have a pH of approximately 5.7 due simply to the dissolved carbon dioxide.
    In a soda drink there is much more carbon dioxide dissolved, and that's why they are so acidic and bad for your teeth even if they are diet.  The pH of a soda drink due to the carbon dioxide dissolved in it is something like pH 3.5.
    Non-pure water has other things dissolved, which reduces the amount of carbon dioxide that can also be dissolved in it, so unless it has something acidic/basic dissolved it actually has a pH closer to 7 than 'pure' water.
    Interestingly, the pH of water gets lower as you increase the temperature, so boiling water has a lower pH than cold water, but it isn't more acidic because the pH of plain water at the temperature you're at is the reference point you always use.
  10. My first grow I used RO water phd and ran into problems early now I'm on my second grow using tap water left open for 24+ hours and I haven't checked my ph at all since I started and I haven't noticed any problems at all. Infact my plants are growing much healthier this time around and my nute schedule hasn't changed at all
  11. GH PH Up is a little less potent then the down. It usually takes me four times more ph up to get the effects I want compared to GH ph down.

    But I run a hydro logic 200, and while it's true what they say, it's nearly impossible to measure a proper ph level when it's just H2O, I get steady readings of 7.8-8.1 with my blue lab ph meter. It's really gonna boil down to the source of whoever is giving you that water. A slight change in the CO 2 levels of the starting water is going to completely change the pH of the finished product...

    Bottom line. Stop buying gallons of water from different places and hook yourself up with a solid RO system. It's one of those essential building blocks that every grower must have at some point. (Especially the hydro growers).
    And hey, best drinking water at you disposal at the turn of a valve!!!

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